Opiate compounds, methods of making and methods of use

ABSTRACT

The present application relates to novel opioid receptor antagonists and agonists, methods of making these compounds, and methods of use thereof.

This application is a Divisional of U.S. Ser. No. 09/623,872, filed Nov.27, 2000, now U.S. Pat. No. 6,429,218, which is a National Stage ofInternational Application PCT/US99/05131, filed on Mar. 09, 1999, whichclaims benefit to U.S. Provisional Application Serial No. 60/077,402,filed on Mar. 10, 1998 and U.S. Provisional Application Serial No.60/107,902, filed on Nov. 10, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel opioid receptor antagonists andagonists, methods of making these compounds, and methods of use.

2. Description of the Background

The opioid receptor system has been extensively studied over the pasteight decades, driven primarily by a search for analgesics that do notpossess the abuse potential associated with morphine. While thesestudies were unsuccessful, our understanding of the opioid system hasincreased tremendously. A significant breakthrough in our understandingof this system came about as a realization that the pharmacology ofopioids is receptor based. From this vantage point, the focus ofresearch turned to identifying receptor subtypes with the ultimate goalof assigning specific physiological function to individual receptors.Today, the receptor system is known to be composed of the three distinctsubtypes OP₁, OP₂, and OP₃ (delta, kappa and mu), as each of these havebeen cloned and been shown to derive from three different chromosomes.For a discussion of opioid receptors, see Kirk-Othmer Encyclopedia ofChemical Technology, Volume 17, Fourth Edition, 1996, pp. 858-881. Thereis however less however as to the number of subtypes within each of themain branches and while much has been learned along these lines, theprocess of assigning function to subtypes is still an area of activeinvestigation.

The opioid receptor system has been extensively studied over the pasteight decades driven primarily by a search for analgesics that do notpossess the abuse potential associated with morphine. While this efforthas been unsuccessful to date, recent studies have highlighted the deltaopioid receptor system as holding the greatest potential for success.Principally, agonists acting through the delta opioid receptor have beenshown to modulate 4 pain while minimizing many of the side-effectsassociated with morphine which acts primarily at the mu opioid receptor.These unwanted side-effects include physical dependence, respiratorydepression, and gastrointestinal motility problems. These findings haveled to a dramatic increase in the research efforts directed toward theproduction of potent, highly delta receptor selective agonists. The bulkof this effort has been in discovering small molecules as opposed topeptides due to their enhanced stability in vivo and their ability topenetrate the central nervous system.

I.

The discovery of potent, highly receptor-selective opioid pureantagonists has been a goal of medicinal chemists for many years.^(1,2)As molecular probes, antagonists have served as useful tools in thestudy of both the structure as well as the physiological functions ofthe highly complex opioid receptor system. Much has been accomplished asevidenced by the elegant work of Portoghese and coworkers over the pastdecade which ultimately has led to the discovery of the naltrexone-basedkappa and delta receptor subtype-selective antagonistsnorbinaltorphimine³ (1, nor-BNI) and naltrindole⁴ (2, NTI),respectively. Following Portoghese's lead, workers at SmithKline Beechamrecently reported that the octahydroisoquinoline (3, SB 205588) was asecond-generation, highly potent and selective delta antagonist formallyderived from naltrindole fragmentation.⁵ One specific research aim hasbeen the discovery of opioid receptor selective reversibly bindingligands from the N-substituted(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4a) class ofcompounds that display pure antagonist activity.⁶ These compounds willbe useful as molecular probes for the opioid receptor as well aspotential drug candidates for the treatment of substance abuse and otherCNS disorders.⁷ While mu antagonists have for years been used in drugabuse therapy, recent findings suggest that kappa antagonists couldprovide a more effective, long-lasting treatment strategy.⁸ A greatvariety of N-substituted derivatives of 4a has been prepared, but untilthe recent demonstration of mu selectivity for 5a,⁹ none had shownselectivity between the opioid receptor subtypes. Since the pureantagonist activity of these compounds is not dependent on theN-substituent, multiple changes to this part of the molecule would beexpected to affect binding affinity and possibly receptor selectivitybut not alter its fundamental antagonist character. This featuredistinguishes this class of antagonist from the morphone-basedcompounds, which display pure antagonist behavior only withN-substituents such as allyl or cyclopropylmethyl but not methyl, ethyl,or phenethyl.¹⁰ It is currently believed that the N-substituent in 4ainteracts with a lipophilic binding domain which has been described aseither very large or quite malleable since a multitude of differenttypes of N-substituent changes provided ligands displaying high bindingaffinity.¹¹ It has also been determined that maximum potency andselectivity for the mu opioid receptor is achieved when theN-substituent incorporates a lipophilic entity (phenyl or cyclohexylring) separated from the piperidine nitrogen by three atoms asillustrated by compounds 5a-d.^(9,11) The synthesis of κ-selectivecompounds remains an important goal.

II.

Derivatives of N-substituted(±)-trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine, such as 6 and 7,are known to posses nonselective potent opioid pure antagonistactivity.¹²⁻¹⁶ Early investigations of the phenylpiperidine class ofopioid antagonists identified the 3-methyl substituent and its transrelative relationship to the 4-substituent as being both necessary andsufficient to impart antagonist activity to the agonist4-(3-hydroxyphenyl)piperidine.¹² This feature distinguished thephenylpiperidines from the oxymorphones which rely on particularN-substituents (i.e. allyl, cyclopropylmethyl) for expression of opioidantagonist activity.¹⁷ Further studies demonstrated that theN-substituent in the phenylpiperidine antagonists controls their potencyand efficacy.¹⁵ Accordingly, there remains a need for compounds whichhave similar therapeutic effects as thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidines, but are based ondifferent structural elements.

III.

Numerous structural types of opioid agonists have been discovered, andseveral such as methadone, meperidine, fentanyl, and pentazocine as wellas others have become important drugs for the treatment of pain.¹⁰However, there are only a few structural types that show potent, opioidpure antagonist activity.^(10,7) A resurgence in heroin use in recentyears coupled with the demonstrated effectiveness of opioid antagonistsfor the treatment of other substances of abuse has spurred new interestin the development of novel antagonists for opioid receptors.¹⁶

The oxymorphone-related compounds such as naloxone (8a) and naltrexone(8b), where the antagonist activity is dependent upon the N-substituent,have received considerable attention over the past few decades.¹⁰ Forexample, pioneering studies by Portoghese and coworkers lead to thedevelopment of the prototypical kappa and delta opioid receptorantagonists, norbinaltorphimine (1, nor-BNI) and naltrindole (2, NTI).In contrast, the N-substitutedtrans-3,4-dimethyl-(3-hydroxyphenyl)piperidine (9a-d) class of pureantagonist has received relatively little attention. Studies with theN-methyl analog 9a as well as many other N-substituted analogs such as9b, 9c (LY255582), and 9d showed that the pure antagonist activity wasdependent on the 3-methyl substituent and its trans relativerelationship to the 4-methyl substituent on the piperidine ring and,unlike the oxymorphone class, was independent of the nature of theN-substituent.^(7,16,7,6,3,14) Interestingly, the 3,4-dimethyl cisisomer 9e was found to be a mixed agonist-antagonist. May andcoworkers¹⁸ reported that 2,9α-dimethyl-5-(3-hydroxyphenyl)morphan(10a), which has the 9-methyl group in a configuration comparable to thecis-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine (9e) with the5-(3-hydroxyphenyl) group locked in an equatorial conformation relativeto the piperidine ring in the morphan structure, was a weak but pureantagonist.

Neither 2,9β-dimethyl-5-(3-hydroxyphenyl)morphan (10b) nor2,4β-dimethyl-5-(3-hydroxyphenyl)morphan (10g) have not been reported,due to a lack of synthetic accessibility to these structural isomers.Accordingly, the successful synthetic preparation of 2,9β-morphans and2,4β-morphans remains an important goal of in the field opioidreceptor-binding compounds.

IV.

In search of analgesics possessing a reduced side-effect profilerelative to morphine, much effort has been expended towards findingopioids which operate via δ or κ opioid receptors as opposed to the gopioid receptor which meditates the actions of morphine and itscongeners.¹⁰ BW373U86 (11)¹⁹ and SNC-80 (12)²⁰ represent one class ofopioid agonists discovered to be selective for the δ opioid receptor.Due to the lack of a clear opioid message substructure (i.e., a tyraminecomponent similar to the enkephalins), compounds 11 and 12 have beenreferred to as non-classical opioid ligands.⁵ The piperazine subunit of11 and 12 is not commonly found in compounds showing activity at theopioid receptors. In contrast, piperidine ring compounds are found inmany different classes of opioids.²⁷ If the internal nitrogen atom incompounds 11 or 12 is transposed with the benzylic carbon, piperidinering analogs such as 13 would be obtained. Even though there are commonstructural elements between structures 11 or 12 and 13, the expecteddifference between in basicity between the piperidinyl amino group of 11or 12 and the di-phenyl substituted amine of 13 is sufficient such thatit cannot be predicted whether similarity to suggest that 13 wouldinteract with opioid receptors similar to 11 or 12. It is alsointeresting to note that compound 13 has some structural elements incommon with cis-3-methylfentanyl (14),^(21,22) a non-classical opioidligand selective for the mu opioid receptor. Accordingly, thepreparation of compound 13 and related structures remains an importantgoal.

References

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(8) Rothman, R. B.; Gorelick, D. A.; Eichmiller, P. R.; Hill, B. H.;Norbeck, J.; Liberto, J. G. An open-label study of a functional opioidkappa antagonist in the treatment of opioid dependence. In Problems ofdrug Dependence, 1997: Proceedings of the 59th Annual ScientificMeeting, The College on Problems of Drug Dependence, Inc., Harris, L. S.Eds.; U. S. Department of Health and Human Services: Rockville, Md.,1997; Vol. 178, pp. 309.

(9) Thomas, J. B.; Mascarella, S. W.; Rothman, R. B.; Partilla, J. S.;Xu, H.; McCullough, K. B.; Dersch, C. M.; Cantrell, B. E.; Zimmerman, D.M.; Carroll, F. I. Investigation of the N-substituent conformationgoverning potency and μ receptor subtype-selectivity in(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonists.J. Med. Chem. 1998, 41(11), 1980-1990.

(10) Aldrich, J. V. Analgesics. In Burger's Medicinal Chemistry and DrugDiscovery, Wolff, M. E. Eds.; John Wiley & Sons, Inc.: 1996; Vol. 3:Therapeutic Agents.

(11) Mitch, C. H.; Leander, J. D.; Mendelsohn, L. G.; Shaw, W. N.; Wong,D. T.; Cantrell, B. E.; Johnson, B. G.; Reel, J. K.; Snoddy, J. D.;Takemori, A. E.; Zimmerman, D. M.3,4-Dimethyl-4-(3-hydroxyphenyl)piperidines: Opioid antagonists withpotent anorectant activity. J. Med. Chem. 1993, 36(20), 2842-2850.

(12) Zimmerman, D. M.; Smits, S.; Nickander, R. Further investigation ofnovel 3-methyl-4-phenylpiperidine narcotic antagonists. In Proceedingsof the 40th Annual Scientfic Meeting of the Committee on Problems ofDrug Dependence, 1978, pp. 237-247.

(13) Zimmerman, D. M.; Smits, S. E.; Hynes, M. D.; Cantrell, B. E.;Leander, J. D.; Mendelsohn, L. G.; Nickander, R. Drug Alcohol Depend.1985, 14, 381-402.

(14) Mitch, C. H.; Leander, J. D.; Mendelsohn, L. G.; Shaw, W. N.; Wong,D. T.; Zimmerman, D. M.; Gidda, S. J.; Cantrell, B. E.; Scoepp, D. D.;Johnson, B. G.; Leander, J. D. J. Med. Chem. 1994, 37, 2262-2265.

(15) Evans, D. A.; Mitch, C. H.; Thomas, R. C.; Zimmerman, D. M.; Robey,R. L. Application of metalated enamines to alkaloid synthesis. Anexpedient approach to the synthesis of morphine-based analgesics. J. Am.Chem. Soc. 1980, 102, 5955-5956.

(16) Kreek, M. J. Opiates, opioids and addiction. Mol. Psychiatry 1996,1(3), 232-254.

(17) Zimmerman, D. M.; Gidda, J. S.; Cantrell, B. E.; Schoepp, D. D.;Johnson, B. G.; Leander, J. D. Discovery of a potent, peripherallyselective trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine opioidantagonist for the treatment of gastrointestinal motility disorders. J.Med. Chem. 1994, 37(15), 2262-2265.

(18) Awaya, H.; May, E. L.; Aceto, M. D.; Merz, H.; Rogers, M. E.;Harris, L. S. Racemic and optically active2,9-dimethyl-5-(m-hydroxyphenyl)morphans and pharmacological comparisonwith the 9-demethyl homologues. J. Med. Chem. 1984, 27, 536-539.

(19) Chang, K. J.; Rigdon, G. C.; Howard, J. L.; McNutt, R. W. A novelpotent and selective nonpeptidic delta opioid receptor agonist,BW373U86. J. Pharm. Exp. Ther. 1993, 267, 852-857.

(20) Calderon, S. N.; Rothman, R. B.; Porreca, F.; Flippen-Anderson, J.L.; McNutt, R. W.; Xu, H.; Smith, L. E.; Bilsky, E. J.; Davis, P.; Rice,K. C. Probes for narcotic receptor mediated phenomena. 19. Synthesis of(+)-4-[(aR)-α-(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide(SNC-80): A highly selective, nonpeptide δ opioid receptor agonist. J.Med. Chem. 1994, 37, 2125-2128.

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(22) Xu, H.; Kim, C.-H.; Zhu, Y. C.; Weber, R. J.; Rice, K. C.; Rothman,R. B. (+)-cis-Methylfentanyl and its analogs bind pseudoirreversibly tothe mu opioid binding site: Evidence for pseudoallosteric modulation.Neuropharmacology 1991, 30, 455-462.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide novel compoundswhich bind to opioid receptors.

It is another object of the present invention to provide novel compoundswhich are opioid receptors antagonists that bind with high affinity.

It is another object of the present invention to provide novel opiatesthat are selective for the kappa receptor as compared to the delta andmu receptors.

It is another object of the present invention to provide novel opiatesthat are selective for the mu and kappa receptors as compared to thedelta receptor.

It is another object of the present invention to provide novel opiatesthat are selective for the delta receptor as compared to the mu andkappa receptors.

It is another object of the present invention to provide novel opiatesthat are pure antagonists at the mu, delta and kappa receptors.

It is another object of the present invention to provide methods ofmaking the novel compounds.

It is another object of the present invention to provide methods oftreating a variety of disease states with the novel opiate compounds ofthe present invention.

The objects of the present invention may be accomplished with compoundsrepresented by formula (I), or pharmaceutically acceptable saltsthereof:

where

R₁ is hydrogen, an alkyl group, an aryl group, or an aralkyl group;

R₂ is hydrogen, an alkyl group, an aryl group, or an alkaryl group; and

R₃ is

each X is, independently, halogen, —OH, —OR, an alkyl group, an arylgroup, —NH, —NHR, —N(R)₂, —CF₃, —CN or —C(O)NH₂, —C(O)NHR, or—C(O)N(R)₂;

each R is, independently, an alkyl group, an aryl group or an alkarylgroup;

n is 0 or an integer from 1 to 5; and

R_(a) is hydrogen or an alkyl group.

The objects above may also be accomplished with compounds represented byformula

(II): or pharmaceutically acceptable salts thereof,

where

R₁ is an alkyl group or aralkyl group; and

R₃, R₄, R₅, R₆ are each, independently, hydrogen, an alkyl group, —OH,—NH₂, —NHR, —N(R)₂, halogen, —OR, —CF₃, —CN, —NO₂, or —NHC(O)R;

each R is, independently, an alkyl group, an aryl group, or an alkarylgroup; and

R₇ is hydrogen or an all group.

The objects of the present invention may be also accomplished withcompounds represented by formula (III), or pharmaceutically acceptablesalts thereof:

where

R₁ is an alkyl group or an aralkyl group;

R₂ is hydrogen, an alkyl group, an aralkyl group, ═O, —NH₂, —NHR,—N(R)₂, —NHC(O)R, —NRC(O)R, —NHC(O)R₅, or —NRC(O)R₅;

R₃ and R₄ may be hydrogen or methyl, with the proviso that when R ismethyl then R₄ is hydrogen and when R₃ is hydrogen then R₄ is methyl;

each R is, independently, an alkyl group, an aryl group, or an alkarylgroup; and

R₅ is

each X is, independently, halogen, —OH, —OR, an alkyl group, an arylgroup, —NH₂, —NHR, —N(R)₂, —CF₃, —CN, —C(O)NH₂, —C(O)NHR, or —C(O)N(R)₂;

each R is, independently, an alkyl group, an aryl group, or an alkarylgroup;

n is 0 or an integer from 1 to 5; and

R_(a) is hydrogen or an alkyl group.

The objects above may be accomplished with compounds represented byformula (IV), or pharmaceutically acceptable salts thereof:

where

R_(a) and R_(b) are each, independently, hydrogen or an alkyl group, orR_(a) and R_(b), together, form a cycloalkyl group;

each X is, independently, an alkyl group;

O is a five- or six-membered aryl or heteroaryl group;

each Z is, independently, an alkyl group, —OH, —OR, halogen, —CF₃, —CN,—NH₂, —NHR, or —N(R)₂;

each R is, independently, an alkyl group, an aryl group, or an alkarylgroup;

each W is an alkyl group;

n is 0 or an integer from 1 to 4;

y is 0 or an integer from 1 to 5;

z is 0 an integer from 1 to 8; and

R₅ is an alkyl group, alkenyl group, or aralkyl group.

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the sane becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Synthesis of compounds represented by formula (II).

FIG. 2: Synthesis of compounds represented by formula (III). (A)synthesis of compounds in which R₃ is methyl (9β-compounds). (B)synthesis of compounds in which R₄ is methyl (4β-compounds).

FIG. 3: Retrosynthetic analysis for the synthesis of compoundsrepresented by formula (IV).

FIG. 4: Synthesis of compounds represented by formula (IV).

FIG. 5: Synthesis of compounds (7) as described in Example 1.

FIG. 6: Data from screening of library described in Example 1 at 100 nMagainst the kappa-selective ligand [³H]U69,593 (percent inhibition).

FIG. 7: Comparison of ratios of radioligand binding and GTPγS assays forcompound 8, naltrexone, nor-BNI, 5d, and 5a-c described in Example 1,the N-trans-cinnamyl derivatives of 4b. The radioligand and GTPγSbinding data for 5a-d were taken from ref. 9 cited in Example 1.

FIG. 8: Synthesis of compounds (7) and (8) as described in Example 2.

FIG. 9: Structural representation of (a) Naltrexone, (b)3,4-dimethyl-4-(3-hydroxyphenyl)piperidine, and (c)8a-methyl-4a-(3-hydroxyphenyl)-octahydrobenzo[e]isoquinoline (Example2).

FIG. 10: Structure of(±)-[2-phenethyl-8a-methyl-4a-(3-hydroxymethyl)]octahydrobenzo[e]isoquinoline(8) HCl described in Example 2 by single crystal X-ray analysis.

FIG. 11: Synthesis of compound (18) as described in Example 3.

FIG. 12: Synthesis of compound (21) as described in Example 3.

FIG. 13: Synthesis of compound (5c) as described in Example 4.

FIG. 14: X-Ray structure of (5b) described in Example 4 drawn using theexperimentally determined coordinates.

FIG. 15: Conformational representation of naltrexone (1b), N-substituted3,4-dimethyl-4-(3-hydroxyphenyl)piperidine, and2-alkyl-9β-5-(3-hydroxyphenyl)morphan. These compounds are described inExample 4.

FIG. 16: Synthesis of compound (17) as described in Example 5.

FIG. 17: Synthesis of compound (3) as described in Example 6.

FIG. 18: Synthesis of 4β-5-phenylmorphans as described in Example 7.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a group of compounds that contain apiperidinyl, or a bridged piperidinyl group. The inventive compoundshave been found to have a variety of different activities when bound toopioid receptors.

Compounds of Formula (I)

In formula (I), R₁ is hydrogen, an alkyl group or an aralkyl group. Asused throughout this disclosure, the terms “alkyl group” or “alkylradical” encompass all structural isomers thereof, such as linear,branched and cyclic alkyl groups and moieties. Unless stated otherwise,all alkyl groups described herein may have 1 to 8 carbon atoms,inclusive of all specific values and subranges therebetween, such as 2,3, 4, 5, 6, or 7 carbon atoms. As used herein, the term “aralkyl group”refers to an aryl moiety bonded to an alkyl radical. The aryl moiety mayhave 6 to 20 carbon atoms. The aryl moiety may contain only carbon andhydrogen atoms. Alternatively, the aryl moiety may contain heteroatoms,for example 1, 2, or heteroatoms (e.g., oxygen, nitrogen, and sulfur). Aparticularly preferred aryl moiety is phenyl-. The alkyl radical of thearalkyl group may as described above when R₁ is an alkyl group. Thealkyl group or moiety and/or the aryl moiety may be substituted.Suitable substituents include halogens (F, Cl, Br and I), alkyl groups(e.g., C₁-C₈), alkoxy groups (e.g., C₁-C₈ alkoxy groups), —CF₃, —CN,—NH₂, —NHR, or —N(R)₂. The R groups are, independently, an alkyl group(such as described for R₁ in formula (I) above), an aryl group (such asphenyl) or an aralkyl group group (such as benzyl). In groups incompounds of formula (I)-(IV) where two R groups are bonded to the sameatom, i.e., —N(R)₂, the R groups may, together, form a cyclic alkylgroup. Such a cyclic alkyl group may, preferably, contain 2 to 8 carbonatoms, with 4 or 5 carbon atoms particularly preferred.

Preferably, R₁ is unsubstituted. In a preferred embodiment, R₁ is aC₁-C₈ alkyl group or a C₆-C₁₀ aryl-C₁-C₈-alkyl group. In a morepreferred embodiment, R₁ is a C₁-C₄ alkyl group or a phenyl-C₁-C₄-alkylgroup. Even more preferably, R₁ is a C₁-C₃ alkyl group or aphenyl-C₁-C₃-alkyl group. Most preferably, R₁ is a methyl group, anisopropyl group, or a phenethyl group.

R₂ in formula (I) may be hydrogen, an alkyl group, an aryl group or analkaryl group. Suitable alkyl and alkaryl groups are as described for R₁above. The aryl group may be as described for the aryl moiety of R₁above. Preferably, R₂ is hydrogen.

R₃ in formula (I) is one of the following groups:

In these groups, the phenyl ring may be unsubstituted (n is 0) orsubstituted with 1, 2, 4, or 5 X groups. each X is, independently,halogen (e.g., chlorine or fluorine), —OH, —OR, an alkyl group (such asdescribed for R₁ in formula (I) above), an aryl group (such as phenyl),—NH₂, —NHR, —N(R)₂, —CF₃, —CN, —C(O)NH₂, —C(O)NHR, or C(O)N(R)₂. The Rgroups are, independently, an alkyl group (such as described for R₁ informula (I) above), an aryl group (such as phenyl) or an aralkyl groupgroup (such as benzyl). Preferred X groups are chlorine, fluorine, —OH,—OCH₃ and —NH₂. Preferably, n is 1. The X group(s) may be located at theortho, meta and para positions. The para position is preferred,especially when X is —OH.

R^(a) in the formulas above may be hydrogen or an alkyl group. Suitablealkyls are as described for R₁ in formula (I) above. Preferably, R_(a)is hydrogen or methyl.

The absolute configuration of the carbon atom to which R₁ is bonded maybe (R) or (S). The (S) configuration is preferred.

The compounds of formula (I) are preferably opiates with preferentialaffinity for the μ/κ opioid receptors and comparably less affinity for δreceptors. In a preferred embodiment, these compounds are pureantagonists. The ratio of affinity for the δ receptor to the κ receptor(δ/κ) may be at least 1.5, preferably at least 2.0, more preferably atleast 20, still more preferably at least 100, even still more preferablyat least 750 and most preferably at least 800. The μ/κ ratio may be0.002 to 500.

The compounds of formula (I) may be prepared using well-known synthetictechniques by condensing an acid of the formula R₃-CO₂H with an aminerepresented by the formula:

The acid is preferably converted into an activated ester in order tocouple with the amine. A BOP ester is preferred. In a particularlypreferred embodiment, a variety of compounds within the scope of formula(I) may be simultaneously synthesized and evaluated usingwell-established combinatorial synthesis techniques, for example, asdescribed in Example 1.

Compounds of Formula (II)

In formula (II), R₁ is an alkyl group or an aralkyl group. These groupsmay be as defined for R₁ in formula (I). In a preferred embodiment, R₁is a C₁-C₈ alkyl group or a C₆-C₁₀ aryl-C₁-C₈-alkyl group. In morepreferred embodiment, R₁ is a C₁-C₄ alkyl group or a phenyl-C₁-C₄-alkylgroup. Even more preferably, R₁ is a C₁-C₂ alkyl group or aphenyl-C₁-C₃-alkyl group. Most preferably, R₁ is a methyl group or aphenethyl group.

R₇ is hydrogen or an alkyl group, preferably an alkyl group. Suitablealkyl groups are as described above for R₁. Preferably, R₇ is methyl.

The substituents R₃, R₄, R₅ and R₆ on the fused aromatic ring may be,independently, hydrogen, an alkyl group, —OH, —NH₂, —NHR, —N(R)₂,halogen (e.g., fluorine and chlorine), —OR, —CF₃, —CN, —NO₂, or—NHC(O)R. The R groups are, independently, an alkyl group (such asdescribed for R₁ in formula (I) above), an aryl group (such as phenyl)or an aralkyl group group (such as benzyl). Methyl and ethyl are themore preferred alkyl groups, and methyl is most preferred. Methoxy is apreferred —OR group. In one embodiment, R₃, R₄, R₅ and R₆ are eachhydrogen. In another embodiment, at most three of R₃, R₄, R₅ and R₆ areother than hydrogen. In another embodiment, at most two of R₃, R₄, R₅and R₆ are other than hydrogen. In yet another embodiment, only one ofR₃, R₄, R₅ and R₆ is other than hydrogen. In an embodiment where thefused aromatic ring contains alkyl groups, one, two or three of R₃, R₄,R₅ and R₆ are alkyl groups.

The stereochemical relationship between R₇ and the hydroxyphenyl groupmay be cis or trans. The cis stereochemistry is preferred. All opticalisomers of these compounds are within the scope of the presentinvention.

The compounds of formula (II) are opiates which are preferably pureopioid receptor antagonists. In a particularly preferred embodiment, theopiates are selective for the mu and/or kappa receptor as compared todelta receptors. The δ/κ selectivity may be at least 2:1, but ispreferably higher, such as at least 5:1, 10:1, 20:1, 25:1, 30:1, or50:1. The δ/μselectivity may be at least 2:1, but is preferably higher,such as at least 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, or 50:1

The compounds of formula (II) may be prepared, for example, as shownFIG. 1. These compounds may also be prepared as described in Examples 2and 3 with appropriate modification of the various R groups.

Compounds of Formula (III)

In formula (III), R₁ may be an alkyl group or an aralkyl group. Thesegroups may be as defined for R₁ in formula (I). In a preferredembodiment, R₁ is a C₁-C₈ alkyl group or a C₆-C₁₀ aryl-C₁-C₈-alkylgroup. In a more preferred embodiment, R₁ is a C₁-C₄ alkyl group or aphenyl-C₁-C₄-alkyl group. Even more preferably, R₁ is a C₁-C₂ alkylgroup or a phenyl-C₁-C₃-alkyl group. Most preferably, R₁ is larger thana methyl group, such as a phenethyl group.

R₂ in these compounds may be hydrogen, an alkyl group, an aralkyl group,═O, —NH₂, —NHR, —N(R)₂, —NHC(O)R, —NRC(O)R, —NHC(O)R₅, or —NRC(O)R₅. Thealkyl or aralkyl group may be as described for R₁ in formula (I). The Rgroups are, independently, an alkyl group (such as described for R₁ informula (I) above), an aryl group (such as phenyl) or an aralkyl groupgroup (such as benzyl). The R₅ group of formula (III) has the samestructure for R₃ in formula (I) discussed above. All of the embodimentsdescribed for R₃ in formula (I) apply to R₅ in formulla (III).Preferably, R₂ is hydrogen, an alkyl group, or an amido group, i.e.,—NHC(O)R₅, or —NRC(O)R₅. More preferably, R₂ is hydrogen or an amidogroup.

R₃ and R₄ may be hydrogen or methyl. However, when R₃ is methyl then R₄is hydrogen and when R₃ is hydrogen then R₄ is methyl.

The compounds of formula (III) are preferably opiates which are opioidreceptor pure antagonists. When R₂ is hydrogen, these compounds have apreferential affinity for the μ receptors, as compared to κ or δreceptors. In this embodiment, the μ/δ selectivity may be at least 2:1,but is preferably higher, e.g., at least 5:1, 10:1, 25:1, 50:1, 100:,150:1 or 200:1. In this embodiment, the μ/κ selectivity may be at least2:1, 5:1, 10:1 or 25:1. When R2 is an amido group, the δ/μ selectivitymay be at least 2:1, but is preferably higher, e.g., at least 5:1, 10:1,25:1 or 50:1.

The compounds of formula (III) may be synthesized, for example, as shownin FIG. 2. The synthesis of compounds in which R₃ is methyl(9β-compounds) is shown in FIG. 2A. Compounds in which R₄ is methyl(4β-compounds) may be synthesized as shown in FIG. 2B. For specificexamples of such preparations, see the following Examples 3-5 and 7.

Compounds of Formula (IV)

R_(a) and R_(b) are each, independently, hydrogen or an alkyl group. Thealkyl group may be as described for R₁ in formula (I). Preferably, R_(a)and R_(b) are ethyl. Alternatively, R_(a) and R_(b), together, form acycloalkyl group. Suitable cycloalkyl groups include those having 3 to 7carbon atoms. Cycloalkyl groups having four or five carbon atoms areespecially preferred.

Each X, if present, may be an alkyl group. Suitable alkyl groups are asdescribed for R₁ in formula (I) above. The number of X groups,determined by the variable n, may be 0, 1, 2, 3 or 4. Preferably, n is0.

The group ◯ is a five- or six-membered aryl or heteroaryl group. Phenylis the preferred aryl group. Suitable heteroaryl groups may have one,two, three or four heteroatoms, e.g., nitrogen, oxygen or sulfur.Specific examples of heteroaryl groups include pyridine, pyridazine,pyrimidine, pyrazine, traiazine (e.g., 1,2,3-; 1,2,4-; 1,3,5-),1,2,4,5-tetrazine, furan, thiophene, oxazole, isothiazole, thiadazole,pyrazole, pyrrole, and imidazole.

Preferably, ◯ is a phenyl group. These compounds are represented by theformula:

Each Z, if present, is, independently, an alkyl group, —OH, —OR,halogen, —CF₃, —CN, —NH₂, —NHR, or —N(R)₂;. The R groups are,independently, an alkyl group (such as described for R₁ in formula (I)above), an aryl group (such as phenyl) or an aralkyl group group (suchas benzyl) Suitable alkyl groups are as described for R₁ in formula (I)above. The number of Z groups, determined by the variable y, may be 0,1, 2, 3, 4, or 5. Preferably, y is 1 or 0. More preferably, y is 0.

Each W, if present, is an alkyl group. Suitable alkyl groups are asdescribed for R₁ in formula (I) above. Preferably, W is a methyl. Thenumber of alkyl groups on the piperdine ring is determined by z. Thevariable z may be 0 or an integer from 1 to 8, inclusive of 2, 3, 4, 5,6, or 7. Preferably, z is 1, 2, or 3. In a preferred embodiment, atleast one W group is bonded to a carbon atom adjacent to the carbon atombearing the diamino substituent. The stereochemical relationship betweenthis W group and the diamino substituent may be cis or trans. Whenmultiple W groups are present on the piperdine ring, the stereochemicalrelationship between W the groups may be cis or trans.

In formula (IV), R₅ is an allyl group, an alkenyl group, or an aralkylgroup. The alkyl group and/or the aralkyl group may be as defined for R₁in formula (I). Preferably, these groups have 1 to 8 carbon atoms, morepreferably 1 to 5 carbon atoms. The alkenyl group may have up to threedouble bonds, more preferably, up to two double bonds, and, mostpreferably, one double bond. An alkenyl group is preferred. Mostpreferably, R₅ is an allyl group.

The compounds formula (IV) are opiates which are preferably agoniststhat are selective for the delta receptor. The δ/μ selectivity may be atleast 2:1, but is preferably higher, e.g., at least 5:1, 10:1, 25:1,50:1, 100:1 or 200:1. The δ/κ selectivity may be at least 2:1, but ispreferably higher, e.g., at least 5:1, 10:1, 25:1, 50:1, 100:1, 200:1,250:1 or 500:1.

The compounds of formula (IV) may be synthesized, for example, inaccordance with the retrosynthetic analysis shown in FIG. 3. An exampleof a reaction sequence to obtain compounds of formula (IV) is shown inFIG. 4. For specific examples of syntheses of compounds of formula (IV),see the Example 6 below.

Compounds (I)-(IV) may be in the form of a pharmaceutically acceptablesalt via protonation of the amine with a suitable acid. The acid may bean inorganic acid or an organic acid. Suitable acids include, forexample, hydrochloric, hydroiodic, hydrobromic, sulfuric, phosphoric,citric, acetic and formic acids.

The receptor selectivities discussed above are determined based on thebinding affinities at the receptors indicated.

The compounds of the present invention may be used to bind opioidreceptors. Such binding may be accomplished by contacting the receptorwith an effective amount of the inventive compound. Of course, suchcontacting is preferably conducted in a aqueous medium, preferably atphysiologically relevant ionic strength, pH, etc.

The inventive compounds may also be used to treat patients havingdisease states which are ameliorated by binding opioid receptors. Suchdiseases states include heroin addiction, pain, i.e., the compounds areused as analgesics. The compounds of the inventive may also be used toreverse mu-induced respiratory depression, as cytostatica agents, asantimigraine agents,as immunomodulators, as immunosuppressives, asantiarthritic agents, as antiallergic agents, as virucides, to treatdiarrhea, as antidepressants, as uropathic agents, as antitussives, asantiadditive agents, as anti-smoking agents, to treat alcoholism, ashypotensive agents, or to treat obesity.

The compounds may be administered in an effective amount by any of theconventional techniques well-established in the medical field. Forexample, the compounds may be administered orally, intraveneously, orintramuscularly. When so administered, the inventive compounds may becombined with any of the well-known pharmaceutical carriers andadditives that are customarily used in such pharmaceutical compositions.For a discussion of dosing forms, carriers, additives, pharmacodynamics,etc., see Kirk-Othmer Encyclopedia of Chemical Technology, FourthEdition, Vol. 18, 1996, pp. 480-590, incorporated herein by reference.The patient is preferably a mammal, with human patients especiallypreferred.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified. In each of the Examples, thenumbering of compounds and references cited are specific to eachExample.

EXAMPLES Example 1 Identification of Opiates Selective for the OpioidReceptors

Summary

A three-component library of compounds was prepared in parallel usingmultiple simultaneous solution phase synthetic methodology. Thecompounds incorporated a(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine group as one of themonomers. The other two monomers, which included N-substituted orunsubstituted Boc protected amino acids and a range of substituted arylcarboxylic acids, were selected to add chemical diversity. Screening ofthese compounds in competitive binding experiments with the kappa opioidreceptor selective ligand [³H]U69,593 led to the identification of a κopioid receptor selective ligand,N-{(2′S)-[3-(4-hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(8, RTI-5989-29). Additional SAR studies suggested that 8 possesseslipophilic and hydrogen bonding sites that are important to its opioidreceptor potency and selectivity. These sites appear to existpredominantly within the kappa receptor since the selectivity arisesfrom a 530-fold loss of affinity of 8 for the mu receptor and an 18-foldincrease in affinity for the kappa receptor relative to the mu-selectiveligand,(+)-N-[trans-4-phenyl-2-butenyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(5a). This degree of selectivity observed in the radioligand bindingexperiments was not observed in the fuctional assay. According to itsability to inhibit agonist stimulated binding of [³⁵S]GTPγS at all threeopioid receptors, compound 8 behaves as a mu/kappa opioid receptor pureantagonist with negligible affinity for the delta receptor.

Chemistry

Coupling of (+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4b)(FIG. 5) with an appropriate tert-butoxycarbonyl-protected amino acid(Boc-protected) followed by removal of the Boc-protecting group withtrifuoroacetic acid (TFA) in methylene chloride followed by reductionusing a tetrahydrofuran (THF) solution of borane-dimethyl sulfidecomplex gave the intermediate amines (6a-k) in 15-78% yields (FIG. 5).These intermediates 6 were subjected to column chromatography orcrystallization as necessary to obtain pure compounds. The finalproducts (7) were prepared in scintillation vials via amide bondformation by coupling with a wide variety of commercially availablecarboxylic acids. A representative list of such carboxylic acids followsthe Experimental section of this Example.Benzotriazol-1-yl-oxy-tris-(dimethylamino)phosphoniumhexafluorophosphate (BOP reagent) in THF was employed as the couplingreagent which provided very clean products after aqueous work-up. Thesecompounds were used directly in screening without additionalpurification. Pure compounds for further SAR analysis were obtained bypurification of library samples or by single compound synthesis byconventional synthetic methodology and characterized by MS, ¹H NMR, andelemental analyses.

Results and Discussion

The results from the screening of the 288-compound library incompetitive binding against the kappa opioid receptor selective ligand[³H]U69,593 are illustrated graphically in FIG. 6. Several compoundsshowed significant inhibition of radioligand binding at 100 nM with 8(plate 4, well 20, 71%) being the best (FIG. 6). The data for %inhibition of [³H]69,593 binding by selected library compounds 8-23 at100 nM are listed in Table 1.

A comparative analysis of the structures related to compounds 9-23,which have less binding affinity relative to 8, readily illustrates theimportance for kappa receptor binding of each structural subunit ofgroup R₃ (Table 1). Compound 9, a diastereomer of 8, where the carbon towhich the R₁ isopropyl group is connected has the oppositestereochemistry, shows less binding affinity (11%) for the opioid kappareceptor. The sensitivity to orientation (R or S) at this stereogeniccenter suggests that the isopropyl group may be working in tandem withanother structural feature of the R₃ unit to both increase binding in 8and decrease binding in 9. The difference in affinity of compounds 8(71%) and 10 (28%) suggests that the 4-hydroxyl substituent in 8 is moreeffective for high kappa binding affinity. Furthermore, the weakerinhibition displayed by compounds 11 (20%) and 12 (25%) possessing metaand ortho hydroxyl substituents respectively, pinpoints the paraplacement of the para-hydroxyl group as the optimum position. The factthat compound 19, which lacks the isopropyl group but has thepara-hydroxyphenylpropionic substituent, shows less affinity (11% vs.71%) relative to 8, adds additional support to the importance of the R₁isopropyl and 4-hydroxyphenyl groups to the kappa-selective binding. Thelow affinity of compound 20 (20%) which has a methyl substituent inposition (R₁) shows that a methyl group may be less effective than theisopropyl group. This strengthens the notion that both the isopropylgroup (R₁) and the 4-hydroxyphenyl group for R₃ are working together toelicit high affinity binding at the kappa opioid receptor in compound 8.The results for compound 13 (6%) suggests that two methylene groups aremore effective between the phenyl ring and the amide carbonyl indiversity element R₃, presumably because the para-hydroxyl group cannotreach its site of interaction in the truncated derivative. Furthermore,the lower inhibition of binding for compound 14 (15%) which incorporatesa trans double bond in the connecting chain shows that the length of thechain is not optimal to impart high binding affinity, implying thatflexibility is also preferred in this carbon chain to provide properligand and receptor alignment. The lower affinity of the 4-fluoroderivative 15 (26%) and the 4-methoxy derivative 18 (16%) supports thesuggestion that a hydrogen bond exists between ligand 8 and the receptorwith compound 8 donating the hydrogen. This is further supported by thelower affinity of the 3,4-dihydroxyl derivative 16 (31%) which canhydrogen bond internally and the 3-methoxy-4-hydroxy derivative 17 (42%)whose hydrogen bond could be sterically encumbered by interference froman adjacent methoxy group. Interestingly, all compounds having methyland not hydrogen as the second diversity element R₂, 21 (0%), 22 (1%),and 23 (7%) displayed very low binding affinity usually at baseline(DMSO blank) levels. Apparently, position R₂ is preferablyunsubstituted. These results suggest that the amide group may be part ofa separate hydrogen-bonding interaction to place the key R₁ isopropyland R₃ p-hydroxyphenyl rings in their correct positions for stronginteraction with the receptor. Alternatively, the N-methyl substituentmay be decrease ligand affinity through repulsive steric interactions.

Taken together, the data suggests that the high binding affinitydisplayed by 8 results from a combination of several structural featurespresent in its N-substituent. These include a 4-hydroxyl group in thependant phenyl ring of group R₃, the length and flexibility of thecarbon chain connecting this ring to the amide carbonyl and the presenceof a beta (position R₁) isopropyl group with an S configuration at theadjacent stereogenic center. The data analysis suggests that theprinciple stabilizing interactions could be related to binding of thehydroxyl and isopropyl substituents with the other atoms of theN-substituent substructure acting to hold these two binding elements inoptimum overlapping positions within the receptor site. Alternatively,the isopropyl group could be acting to bias the conformation of moleculeto provide the best alignment of the 4-hydroxyphenylpropionic acidside-chain with its binding site.

In order to gain additional SAR information, a pure sample of 8 alongwith compounds 24-27 which vary at the R₁ position alone was preparedfor study. Table 2 lists the K_(i) values for these derivatives at themu and kappa opioid receptors along with the K_(i) values for themu-selective reference compound 5a, naltrexone, and the kappa-selectiveantagonist nor-BNI. The delta receptor assay was not performed forcompounds 24-27 as all previous derivatives of 8 had shown no affinityfor this receptor subtype. This study revealed that 8 not only activelybinds the kappa receptor (K_(i)=6.9 nM) but also possessed a 57-foldselectivity for the kappa vs. the mu receptor (K_(i)=393 nM)and >870-fold selectivity for the kappa vs. the delta receptor(K_(i)>5700 nM). Compound 8 thus displays a high degree of opioid kappareceptor subtype selectivity.^(1,2) Nor-BNI (1) has a higher affinityfor the kappa receptor than 8 and has a greater kappa selectivityrelative to the mu receptor. However, 8 is more selective for the kappareceptor relative to the delta receptor. A part of these differencescould be due to the use of different tissues and radioligands.

The data for the beta isobutyl substituent compound 24, which resultsformally from insertion of a methylene between the isopropyl group andits adjacent stereogenic center of compound 8, displays a loss ofaffinity for the kappa receptor while maintaining the same affinity forthe mu receptor as compound 8. The net effect is a loss of selectivitybetween the mu and kappa receptor subtypes. Compound 26 (R₁=cyclohexyl)shows a similar loss of affinity for the kappa receptor with a gain inaffinity for the mu receptor resulting in a similar loss of selectivity.Compound 25 with an R₁ sec-butyl group shows a slight decrease in bothkappa and mu potency but retains selectivity, though its magnitude islower relative to 8. Compound 27 (R₁=benzyl) displayed a binding profilecompletely different from that seen in 8 with a tremendous increase inmu potency and concomitant loss of kappa potency. This was notunexpected since compound 27, prepared from the amino acidphenylalanine, possesses an N-substituent with a phenyl ring separatedfrom the piperidine ring by three methylene groups which are known tofavor mu binding.^(1,2) It was for this reason that phenylalanine wasexcluded from use in the library synthesis. Overall, the behaviors ofthe various R₁ derivatives of 8 indicate that the size of the lipophilicgroup in position R₁ is important to both the potency and receptorsubtype selectivity of the ligand. Furthermore, the data supports thehypothesis that the isopropyl group in 8 is not simply biasing theconformation of side-chain but is instead interacting with the receptordirectly in a ligand stabilizing interaction.

The agonist/antagonist activity of compound 8 was measured bydetermining its ability to either stimulate or reverse opioid agoniststimulated binding of the nonhydrolyzable GTP analog, [35S]GTPγS, in allthree opioid receptor assays (Table 3).³ Table 3 includes data obtainedfor naltrexone, the standard nonselective opioid pure antagonist,nor-BNI, the prototypical kappa-selective antagonist, and the potent,mu-favoring opioid antagonist (5a). The kappa selectivity displayed bycompound 8 in the inhibition of radioligand binding assay was notobserved in the [³⁵S]GTPγS functional assay. This is not an atypicalsituation; radioligand binding results often differ substantially fromthose seen in functional assays but this typically involves agonists.The antagonists, naltrexone, normally display K_(i) (radioligand)/K_(i)(GTPγS) binding ratios near unity whereas ratios greater than unity havebeen observed for antagonists of the N-substitutedtrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine series.¹ Thisphenomenon is illustrated graphically in FIG. 7. The trans-cinnamylderivatives 5a-c and compound 5d display K_(i) (radioligand)/K_(i)(GTPγS) binding ratios greater than unity in the mu and kappa receptorassays which is distinctly different from the response demonstrated bynaltrexone. In the present case compound 8 is found to behave likenaltrexone in the kappa receptor assays with a ratio near unity which isfar different from the behavior seen for 5a-c and 5d, which show ratiosof 118, 228, 63, and 85, respectively. In the mu receptor assay on theother hand, compound 8 with a ratio of 54 behaves like 5a-c and 5d whichgive ratios of 19, 66, 43, and 15. This differential response of 8 inthe [³⁵S]GTPγS assay is sufficiently large so as to erode the kappareceptor selectivity observed for 8 in the radioligand binding assays.Note that the K_(i) (radioligand)/K_(i) (GTP) binding ratios for nor-BNIat the mu and kappa receptor are 2.8 and 7.36, respectively.

Conclusions

The identification of compound 8, which displays a highly selectivekappa vs. mu receptor inhibition of radioligand binding profile and apotent mu/kappa opioid antagonist profile, demonstrates theeffectiveness of the biased library approach to lead compoundgeneration. Since both the mu and kappa receptors may be important inheroin abuse, compound 8 should be useful as a treatment medication forheroin abuse.

Experimental Section

Melting points were determined on a Thomas-Hoover capillary tubeapparatus and are not corrected. Elemental analyses were obtained byAtlantic Microlabs, Inc. and are within ±0.4% of the calculated values.All optical rotations were determined at the sodium D line using aRudolph Research Autopol III polarimeter (1-dm cell). ¹H NMR spectrawere determined on a Bruker WM-250 spectrometer using tetramethylsilaneas an internal standard. Silica gel 60 (230-400 mesh) was used for allcolumn chromatography. Mass spectral data was obtained using a FinneganLCQ electrospray mass spectrometer in positive ion mode at atmosphericpressure. All reactions were followed by thin-layer chromatography usingWhatman silica gel 60 TLC plates and were visualized by UV, charringusing 5% phosphomolybdic acid in ethanol and/or exposure to iodinevapor. All solvents were reagent grade. Tetrahydrofuran and diethylether were dried over sodium benzophenone ketyl and distilled prior touse. Methylene chloride was distilled from calcium hydride prior to use.

General Method for the Introduction of Diversity Elements R₁ and R₂ intoStructure 6. (+)-(3R,4R)-Dimethyl-4-(3-hydroxyphenyl)piperidine (4b)(11.5 mmol), the appropriate Boc-protected amino acid (11.5 mmol) andBOP reagent (11.5 mmol) were combined in THF (150 mL) at roomtemperature, and to this was immediately added triethylamine (TEA) ordiisopropylethylamine (25.3 mmol). After stirring for 1 h, the reactionmixture was poured into ethyl ether (500 mL) and water (150 mL) in aseparatory funnel. The mixture was shaken and the aqueous layer removed.This procedure was repeated using 150 mL saturated NaHCO₃ and 150 mLbrine. The organic layer was diluted with hexane until cloudy and dried(Na₂SO₄), concentrated under reduced pressure, then dissolved in 100 mLchloroform (stored over K₂CO₃), and concentrated again. This was placedon a high vacuum system to remove residual solvent yielding a foamyyellow/white solid.

After remaining under vacuum on the pump overnight, this unpurifiedmaterial was dissolved in methylene chloride 45 mL and cooled to −20° C.(methanol/ice). To this was added neat trifluoroacetic acid in 10-mLportions over 2 min to give a total addition of 30 mL. The entiremixture was stirred for exactly 30 min and then the cooling bath wasremoved for exactly 30 min. At this point, the reaction mixture waspoured into a 1 L beaker containing a large stir bar and a rapidlyagitated mixture of saturated bicarbonate solution (400 mL) andchloroform (150 mL). After completed addition, the pH of the mixture wasverified to be 10 and adjusted with solid sodium bicarbonate ifnecessary. This mixture was poured into a separatory funnel. Anyprecipitated organic compounds were rinsed into the separatory funnelusing a small amount of methanol. The beaker was then rinsed with asmall amount of water which was added to the separatory funnel. Thelayers were agitated, separated, and the aqueous layer extracted fiveadditional times using 3:1 methylene chloride:THF. It was observed thatcompounds with small groups R₁ required additional extractions and/orsodium chloride saturation of the aqueous layer. The combined organiclayers were dried over sodium sulfate and the solvent removed at reducedpressure. The material was then placed on a high vacuum pump to yield ayellow foamy solid.

Unpurified material from the deprotection step was dissolved in THF (150mL) and cooled to −20° C. (methanol/ice). To this stirred mixture wasadded a solution of borane dimethylsulfide complex, 2M in THF (110 mmol)dropwise. The solution was then heated to reflux and held for 3 h afterwhich time, the solution was cooled to −20° C., and to this wascarefully added methanol (72 mL) dropwise. This mixture was stirred for1 h at room temperature, 16.4 mL of 1M HCl in ethyl ether was added, thesolution was allowed to stir for 30 min, and the solvents removed on arotary evaporator. The resulting residue was partitioned between 3:1methylene chloride:tetrahydofuran and water, the pH was adjusted to withsaturated sodium bicarbonate, and the aqueous layer was saturated withsodium chloride and extracted several times with 3:1 methylenechloride:tetrahydofuran. The combined organic layers were dried oversodium sulfate and the solvent removed. This material was purified byflash chromatography on a silica gel column which was prepared by slurrypacking with chloroform. The impure compounds were loaded on the columnas a chloroform solution. Elution proceeded with neat chloroformfollowed by 3% methanol up to 10% methanol in chloroform as needed toelute the desired compounds. Product fractions were combined and thesolvent was removed on a rotary evaporator. This material was dissolvedin a minimum of hot ethyl acetate and allowed to crystallize.Crystalline material was isolated by filtration followed by washing witha small amount of ice-cold ethyl acetate and used directly in the nextstep after drying overnight in a vacuum oven.

Introduction of Diversity Element R₃ into Structure 7. The appropriatepure diamine 6, produced in the previous step (0.05 mmol×the number ofderivatives being prepared), was dissolved in THF (2 mL×the number ofderivatives being prepared) and to this was added TEA (0.1 mmol×thenumber of derivatives being prepared). Then, into prelabeled, 20-mLscintillation vials containing a stir bar was added one of the chosencarboxylic acids (0.05 mmol). To this was added the appropriate fractionof the diamine/TEA/THF mixture followed by 50 μL of a 1M solution of BOPreagent in dimethylformamide (DMF). The vial was then capped with atelfon-lined lid and stirred for 1 h at room temperature. After thistime, 4 mL of ethyl ether and 2 mL of water were added to the vial.After shaking and allowing the layers to settle, the aqueous layer waswithdrawn with a pipette. Next, 2 mL of saturated sodium bicarbonatesolution was added and the procedure repeated. This was followed by asimilar wash with saturated sodium chloride solution. Sodium sulfate wasadded to the vial, and after drying, the mixture was pipetted into apreweighed, prelabeled 20-mL scintillation vial via a 6-in Pasteurpipette containing a small cotton plug. Following this, 2 mL ofchloroform was added to the drying agent and the vial shaken after whichthe chloroform rinse was filtered as above. The collecting vials wereplaced under a nitrogen outlet and allowed to evaporate. Once thesolvent was removed, the vials were placed in a high vacuum desiccatorand allowed to remain overnight. The vials were reweighed, and the crudeyield determined by difference. Since pilot studies showed that theBOP-coupling reaction produced very clean samples, the products wereused without further purification, and the purity was taken to be 100%.

Prior to screening, all compounds were diluted to a concentration of 10mM in dimethylsulfoxide (DMSO). Dilution was accomplished by determiningthe mean mmol/vial for each batch of 20 reactions using an Excel 3.0spreadsheet. Weights deviating from the mean by >±10% were grouped intoa second and third set above and below the mean. These were alsoaveraged within the same parameters. Any compounds not falling withinthe above sets were diluted individually according to their weight. Thisprocedure permitted sample dilution to be accomplished using a minimumnumber of different volume deliveries of DMSO. Once diluted to 10 mM,1-mL samples from each vial were withdrawn and placed in rows A and E(one compound/well) of a 1 mL×96-well polypropylene microtiter plate.Serial dilution was then performed using Matrix multichannel pipettorswhich provided a 1-mM solution in rows B and F and a 0.1-mM solution inrows C and G. Once all of the compounds were transferred to plates anddiluted to the proper concentration, the plates were placed in therefrigerator prior to assay.

N-(2′-Aminoethyl)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (6a).Prepared from N-(tert-butoxy)-glycine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 15% yield: ¹H NMR (MeOH-d4) δ 7.13-7.062 (t, 1H,J=8.1 Hz), 6.77-6.74 (m, 2H), 6.59-6.55 (m, 1H), 3.31-3.29 (m, 1H),2.83-2.70 (m, 3H), 2.5 (d, 2H, J=3.1 Hz), 2.46-2.27 (m, 3H), 2.00 (s,1H), 1.6 (d, 2H, J=3.1 Hz), 1.68 (d, 1H, J=13.7 Hz), 1.29 (s, 3H), 0.89(d, 3H, J=7.0 Hz); ¹³C NMR (MeOH-d4) δ 158.5, 152.9, 130.0, 117.9,113.9, 113.3, 61.6, 57.1, 51.5, 40.2, 39.5, 39.1, 32.0, 28.2, 16.7. MS(electrospray) M+1=249. Calculated=249.

N-(2′-Methylaminoethyl)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6b). Prepared from N-(tert-butoxy)-sarcosine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 32% yield: ¹H NMR (MeOH-d4) δ 7.9 (t, 1H, J=7.7Hz), 6.77 (d, 1H), 6.74 (s, 1H), 6.58 (d, 1H), 2.95-2.90 (m, 1H),2.87-2.82 (m, 2 26 (dd, 1H), 2.61-2.55 (m, 2H), 2.54 (s, 3H), 2.52 (td,1H), 2.37 (td, 1H), 2.03-2.00 (m, 1H), 1.69 (brd, 1H), 1.30 (s, 3H),0.89 (d, 3H, J=7.0 Hz); ¹³C NMR (MeOH-d4) δ 130.0, 118.0, 113.8, 113.3,57.4, 56.7, 51.1, 48.2, 40.2, 39.4, 35.0, 31.9, 28.1, 16.6. MS(electrospray) M+1=263. Calculated=263.

N-[(2′S)-Aminopropyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6c). Prepared from N-(tert-butoxy)-L-alanine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 56% yield: ¹H NMR (MeOH-d4) δ 7.11-7.08 (t, 1H,J=7.7), 6.78-6.76 (d, 1H), 6.74 (s, 1H), 6.59-6.57 (d, 1H), 2.953-2.902(m, 1H), 2.874-2.826 (m, 2H), 2.676-2.647 (dd, 1H), 2.618-2.559 (m, 2H),2.548 (s, 3H), 2.541-2.400 (td, 1H), 2.342-2.284 (td, 1H), 2.030-2.002(m, 1H), 1.613-1.587 (brd, 1H), 1.303 (s, 3H), 0.800-0.786 (d, 3H,J=7.0); ¹³C NMR (MeOH-d4) d 130.0, 118.0, 113.8, 113.3, 57.4, 56.7,51.1, 48.2, 40.2, 39.4, 35.0, 31.9, 28.1, 16.6. MS (electrospray)M+1=263. Calculated=263.

N-[(2′S)-(Methylamino)propyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6d). Prepared from N-(tert-butoxy)-N-methyl1-alanine¹⁷ and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 33% yield: ¹H NMR (MeOH-d4) δ 7.18 (t, 1H, J=7.9Hz), 6.76 (d, 1H), 6.73 (s, 1H), 6.57 (d, 1H), 2.72-2.64 (m, 2H),2.61-2.47 (m, 3H), 2.36 (s, 3H), 2.34-2.20 (m, 3H), 2.00-1.99 (m, 1H),1.56 (dd, 1H), 1.29 (s, 3H), 1.03 (d, 3H, J=6.2 Hz), 0.65 (d, 3H, J=6.9Hz); ¹³C NMR (MeOH-d4) δ 158.4, 153.3, 130.1, 117.9, 113.7, 113.3, 65.1,56.0, 52.9, 52.9, 40.0, 39.5, 33.7, 31.9, 28.0, 17.3, 16.7. MS(electrospray) M+1=277. Calculated=277.

N-[(2′S)-Amino-3′-methylbutyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6e). Prepared from N-(tert-butoxy)-L-valine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 78% yield: ¹H NMR (MeOH-d4) δ 7.126-7.062 (t, 1H),6.769-6.735 (m, 2H), 6.603-6.558 (m, 1H), 2.657-2.179 (m, 8H), 2.000(brs, 1H), 1.583-1.502 (m, 2H), 1.294 (s, 3H), 0.978-0.912 (q, 6H),0.789-0.761 (d, 3H); ¹³C NMR (MeOH-d4) δ 158.5, 153.3, 130.1, 117.8,113.8, 113.3, 63.4, 55.8, 54.1, 53.3, 40.0, 39.5, 33.1, 31.9, 28.1,19.6, 19.2, 16.8. MS (electrospray) M+1=291. Calculated=291.

N-[(2′R)-Amino-3′-methylbutyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6f). Prepared from N-(tert-butoxy)-D-valine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 62% yield: ¹H NMR (MeOH-d4) δ 7.11-7.08 (t, 1H),6.78-6.76 (d, 1H), 6.74 (s, 1H), 6.59-6.57 (dd, 1H), 3.139-3.097 (m,1H), 2.953 (brs, 1H), 2.894-2.865 (dd, 1H), 2.546-2.500 (m, 2H),2.401-2.292 (m, 3H), 2.046-2.034 (brm, 1H), 1.894-1.827 (sext, 1H),1.62-1.30 (m, 1H), 1.311 (s, 3H), 1.042-1.006 (dd, 6H), 0.834-0.820 (d,3H); ¹³C NMR (MeOH-d4) δ 152.9, 130.1, 118.0, 113.8, 113.3, 59.8, 58.8,55.2, 50.0, 40.4, 39.4, 31.6, 31.1, 28.0, 18.8, 18.5, 16.5. MS(electrospray) M+1=291. Calculated=291.

N-[(2′S)-Amino-4′-methylpentyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6g). Prepared from N-(tert-butoxy)-L-leucine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 56% yield: ¹H NMR (MeOH-d4) δ 7.09 (t, 1H, J=7.9Hz), 6.76 (d, 1H, J=7.9 Hz), 6.73 (s, 1H), 6.57 (dd, 1H, J=2.2, 7.9 Hz),3.03-2.97 (m, 1H), 2.73 (d, 1H, J=11.2 Hz), 2.64 (d, 1H, J=11.1 Hz),2.56 (td, 1H, J=2.5, 12.0 Hz), 2.48 (dd, 1H, J=2.7, 11.4 Hz), 2.33 (td,1H, J=4.5, 12.7 Hz), 2.25 (dd, 1H. J=3.6, 12.4 Hz), 2.19-2.15 (m, 1H),2.01-2.00 (m, 1H), 1.75 (sept, 1H, J=6.6 Hz), 1.56 (d, 1H. J=13.0 Hz),1.29 (s, 3H), 1.27-1.15 (m, 2H), 0.94-0.91 (m, 6H), 0.07 (d, 3H, J=7.0Hz); ¹³C NMR (MeOH-d4) δ 158.3, 153.3, 130.1, 117.9, 113.7, 113.2, 65.7,56.0, 53.1, 46.5, 45.2, 40.0, 39.5, 31.9, 28.0, 25.8, 23.7, 22.6, 16.7.MS (electrospray) M+1=305. Calculated=305.

N-[(2′S)-Amino-3′-methylpentyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6h). Prepared from N-(tert-butoxy)-L-isoleucine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 47% yield: ¹H NMR (MeOH-d4) δ 7.19 (t, 1H, J=7.9Hz), 6.76 (d, 1H, J=8.1 Hz), 6.73-6.73 (m, 1H), 6.58-6.56 (dd, 1H,J=2.1, 7.9 Hz), 2.86-2.82 (m, 1H), 2.75-2.73 (m, 1H), 2.65-2.57 (m, 2H),2.502-2.474 (dd, 1H, J=2.8, 11.4 Hz), 2.40-2.23 (m, 3H), 2.02-2.00 (m,1H), 1.59-1.50 (m, 2H), 1.46-1.41 (m, 1H), 1.30 (s, 3H), 1.24-1.17 (m,1H), 0.98-0.87 (m, 6H), 0.78 (d, 3H, J=7.0 Hz); ¹³C NMR (MeOH-d4) δ158.3, 153.2, 130.1, 117.9, 113.7, 113.3, 61.9, 55.9, 53.1, 52.9, 49.0,40.0, 39.5, 39.3, 31.9, 28.0, 26.6, 16.7, 15.1, 11.8. MS (electrospray)M+1=305. Calculated=305.

N-[(2′S)-Amino-2′-cyclohexylethyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6i). Prepared from N-(tert-butoxy)-L-cyclohexylglycine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 63% yield: ¹H NMR (MeOH-d4) δ 7.18 (t, 1H. J=7.9),6.76 (d, 1H, J=7.8 Hz), 6.75 (s, 1H), 6.57 (d, 1H, J=7.8 Hz), 2.74-2.70(m, 2H), 2.63-2.55 (m, 2H), 2.47-2.45 (d, 1H, J=10.0 Hz), 2.48 (dd, 1H,J=2.9, 12.4 Hz), 2.36 (td, 1H, J=4.3, 12.6 Hz), 2.23 (t, 1H, J=11.6 Hz),2.00 (m, 1H), 1.76-1.74 (m, 3H), 1.67 (d, 2H, J=11.9 Hz), 1.57 (d, 1H.J=13.0 Hz), 1.39-1.16 (m, 7H), 1.09 (quint, 2H, J=12.4 Hz), 0.77 (d, 3H,J=6.8 Hz); ¹³C NMR (MeOH-d4) δ 158.3, 153.3, 130.1, 117.9, 113.7, 113.3,162.6, 55.8, 53.4, 53.1, 42.9, 40.0, 39.5, 31.9, 30.9, 30.5, 30.2, 28.0,27.6, 27.4, 16.7. MS (electrospray) M+1=331. Calculated=331.

N-[(2′S)-Methylamino-2′-phenylethyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6j). Prepared from N-(tert-butoxy)-N-methyl-phenylglycine¹⁷ and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 44% yield: ¹H NMR (MeOH-d4) δ 7.34-7.22 (m, 5H),7.13 (t, 1H, J=8.2 Hz), 6.80-6.77 (m, 2H), 6.61-6.69 (m, 1H), 3.63 (dd,1H, J=3.7, 12.6 Hz), 2.73 (brd, 2H, J=7.6 Hz), 2.64-2.52 (m, 3H), 2.38(dd, 2H, J=3.6, 12.6 Hz), 2.25 (s, 3H), 2.04 (brd, 1H, J=6.3 Hz), 1.59(d, 1H, J=12.9), 1.312 (s, 3H), 0.818-0.790 (d, 3H, J=6.9); ¹³C NMR(MeOH-d4) δ 147.3, 142.5, 131.5, 119.5, 119.0, 118.0, 107.4, 103.2,102.7, 68.7, 68.233, 67.7, 55.2, 52.9, 45.1, 42.5, 42.5, 29.2, 28.9,24.2, 21.3, 17.7. MS (electrospray) M+1=339. Calculated=339.

N-[(2′S)-Amino-3′-phenylpropyl]-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(6k). Prepared from N-(tert-butoxy)-L-phenylalanine and(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine according to thegeneral procedure in 44% yield: ¹H NMR (MeOH-d4) δ 7.29 (t, 1H, J=7.4Hz), 7.24-7.06 (m, 5H), 6.75-6.71 (m, 2H), 6.57-6.55 (m, 1H), 3.86-3.84(m, 5H), 3.22-3.94 (m, 1H), 2.83-2.69 (m, 2H), 2.63-2.39 (m, 5H),2.35-2.24 (m, 2H), 1.97 (t, 1H, J=6.4 Hz), 1.54 (t, 1H, J=12.7 Hz), 1.27(s, 3H), 0.74 (dd, 3H, J=6.95, 21.04 Hz); ¹³C NMR (MeOH-d4) δ 158.3,153.3, 139.9, 130.6, 130.3, 130.0, 129.6, 129.2, 127.5, 127.1, 118.0,117.9, 113.8, 113.7, 113.2, 65.0, 64.7, 61.0, 57.3, 56.1, 52.9, 52.1,50.5, 49.5, 49.3, 49.2, 49.0, 48.8, 48.7, 48.5, 41.9, 41.5, 40.3, 40.0,39.4, 31.9, 28.0, 16.7. MS (electrospray) M+1=339. Calculated=339.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(8). Prepared from compound 6e and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure above in 74% yield and purified bysilica gel chromatography. The hydrochloride salt was prepared using 1MHCl in ethyl ether/methanol and precipitated from ethyl acetate: mp136-140° C.; ¹H NMR (free base). CD3OD δ 7.16 (t, J=7.94, Hz, 1H), 7.04(d, J=8.45 Hz, 2H), 6.76 (d, J=7.78 Hz, 1H), 6.72-6.69 (m, 2H), 6.65(dd, J=8.04, 1.76 Hz, 1H), 4.02-3.98 (m, 1H), 3.57 (d, J=12.5 Hz, 1H),3.40 (ddd, J=2.90, 11.6, 13.4 Hz, 2H), 3.03 (dd, J=10.5, 13.4 Hz, 1 Hz),2.84 (t, 7.07 Hz, 2H), 2.60 (t, 7.58 Hz, 2H), 2.43 (dt, J=13.21, 4.9 Hz,1H), 2.36-2.35 (m, 1H), 1.85 (d, J=14.5 Hz, 1H), 1.87-1.76 (m, 1H), 1.42(s, 3H), 0.92 (t, J=6.98 Hz, 6H), 0.815 (d, J=7.53, 3H); ¹³C NMR, CD3ODδ 176.3, 159, 157.7, 153.8, 133.8, 131.3, 131.0, 118.9, 117.1, 114.6,114.2, 62.0, 57.2, 53.2, 52.8, 40.9, 40.3, 33.1, 33.1, 32.5, 31.7, 28.8,20.6, 18.9, 17.3. MS (electrospray) M+1=439. Anal.(C₂₇H₃₉ClN₂O₃.1.5H₂O): C, H, N.

Compounds cited in Table 1 were removed from the library and purified bysilica gel chromatography. The purity of the library sample wasdetermined according to the formula [(mg isolated sample/mg crude masssample) X 100].

N-{(2′R)-[3-(4-Hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(9). Prepared from compound 6f and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (85%); ¹H NMR (MeOH-d4) δ7.83 (s, 3H), 7.13-7.00 (m, 3H), 6.77-6.67 (m, 4H), 6.61-6.57 (m, 1H),3.96-3.89 (m, 1H), 2.86-2.78 (m, 3H), 2.62-2.58 (m, 1H), 2.48 (d, 3H,J=8.0 Hz), 2.36-2.14 (m, 4H), 1.94 (brd, 1H, J=6.3 Hz), 1.76 (sept, 1H,J=5.5 Hz), 1.51 (brd, 1H, J=11.0 Hz), 1.26 (s, 3H), 0.84-0.74 (m, 9H).MS (electrospray) M+1=439. Calculated=439.

N-{(2′S)-[(3-Phenylpropanamido)-3′-methyl]butyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(10). Prepared from compound 6e and 3-phenylpropionic acid according tothe general procedure. Purity (87%); ¹H NMR (MeOH-d4) δ 7.25-7.22 (m,2H), 7.17-7.13 (m, 4H), 6.82 (s, 1H), 6.76 (d, 1H, J=7.8 Hz), 6.70-6.68(m, 1H), 5.74 (s, 1H), 4.02-3.97 (m, 1H), 2.99-2.87 (m, 2H), 2.74-2.69(m, 1H), 2.64 (brd, 1H, J=1.3 Hz), 2.57-2.40 (m, 6H), 2.27-2.21 (m, 2H),2.17 (s, 3H), 1.92-1.87 (m, 2H), 1.56 (d, 1H, J=13.0 Hz), 1.28 (s, 3H),0.81 (t, 6H, J=6.8 Hz), 0.69 (d, 3H, J=6.8 Hz). MS (electrospray)M+1=423. Calculated=423.

N-{(2′S)-[3-(3-Hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(11). Prepared from compound 6e and 3-(3-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (84%); ¹H NMR (MeOH-d4) δ7.24-7.23 (m, 1H), 7.13-7.03 (m, 3H), 6.76-6.57 (m, 5H), 3.32-3.29 (m,4H), 2.85-2.17 (m, 8H), 1.97 (brs, 1H), 1.75-1.73 (m, 1H), 1.57 (brd,1H, J=12.3 Hz), 1.28 (s, 3H) 0.863 (t, 6H, J=6.5 Hz), 0.72 (d, 3H,J=7.0). MS (electrospray) M+1=439. Calculated=439.

N-{(2′S)-[3-(2-Hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(12). Prepared from compound 6e and 3-(2-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (85%); ¹H NMR (CDCl3-d) δ7.04-6.82 (m, 3H), 6.66-6.65 (m, 2H), 6.48-6.39 (m, 3H), 3.97-3.94 (m,1H), 2.87-2.84 (m, 2H), 2.76 (d, 1H, J=11 Hz), 2.56-2.22 (m, 8H),1.94-1.93 (brm, 1H), 1.80 (sextet, 1H, J=6.9 Hz), 1.52 (d, 1H, J=13.3Hz), 1.26 (s, 3H), 0.84 (dd, 6H, J=13:1 Hz), 0.75 (d, 3H, J=6.9 Hz). MS(electrospray) M+1=439. Calculated=439.

N-{(2′S)-[(4-Hydroxyphenyl)acetamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(13). Prepared from compound 6e and 4-hydroxyphenylacetic acid accordingto the general procedure. Purity (88%); ¹H NMR (MeOH-d4) δ 7.14-7.06 (m,3H), 6.67-6.69 (m, 4H), 6.58 (d, 1H, J=8.1 Hz), 3.95-3.92 (m, 1H),3.32-3.30 (m, 2H), 2.70-2.60 (m, 1H), 2.56-2.47 (m, 1H), 2.41-2.15 (m,6H), 1.90 (brs, 1H), 1.81-1.74 (m, 1H), 1.51 (d, 2H, J=12.5 Hz), 1.25(s, 3H), 0.86 (t, 6H, J=6.7 Hz), 0.67 (d, 3H, J=6.9 Hz). MS(electrospray) M+1=425. Calculated=425.

N-{(2′S)-[trans-3-(4-Hydroxyphenyl)acrylamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(14). Prepared from compound 6e and trans-3-(4-hydroxyphenyl)cinnamicacid according to the general procedure. Purity (85%); ¹H NMR (MeOH-d4)δ 7.25-7.37 (m, 3H), 7.11-7.04 (m, 1H), 6.79-6.72 (m, 4H), 6.56 (d, 1H,J=9.5 Hz), 6.47 (d, 1H, J=12.7 Hz), 4.10 (m, 1H), 2.80 (m, 1H), 2.64 (m,1H), 2.54-2.26 (m, 5H), 1.95 (m. 2H), 1.56 (d, 1H, J=13.1), 1.28 (s,3H), 0.94 (t, 6H, J=6.8 Hz), 0.70 (d, 3H, J=6.9). MS (electrospray)M+1=437. Calculated=437.

N-{(2′S)-[3-(4-Fluorophenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(15). Prepared from compound 6e and 3-(4-fluorophenyl)propionic acidaccording to the general procedure. Purity (89%); ¹H NMR (MeOH-d4) δ7.2;3-717.1 (m, 2H), 7.69 (t, 1H, J=8.0 Hz), 6.99-6.92 (m, 2H),6.99-6.92 (m, 2H), 6.76-6.73 (m, 2H), 6.60-6.54 (m, 1H), 3.96-3.90 (m,1H), 2.88 (t, 2H, J=7.7), 2.76 (d, 1H, J=10.3 Hz), 2.65-2.32 (m, 8H),1.97 (brs, 1H), 1.73-1.69 (m, 1H), 1.54 (d, 1H, J=12.1 Hz, 1.27 (s, 3H),0.80 (t, 6H, J=5.8 Hz), 0.71 (d, 3H, J=6.9 Hz). MS (electrospray)M+1=441. Calculated=441.

N-{(2′S)-[3-(3,4-Dihydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(16). Prepared from compound 6e and 3-(3,4-dihydroxyphenyl)propionicacid according to the general procedure. Purity (78%); ¹H NMR (MeOH-d4)δ 7.09 (t, 1H, J=7.9 Hz), 6.76-6.73 (m, 2H), 6.67-6.49 (m, 4H), 3.92(brs, 1H), 2.74 (t, 3H, J=7.6 Hz), 2.63-2.59 (m, 1H), 2.51-2.15 (m, 7H),1.94 (brs, 1H), 1.75-1.70 (m, 1H), 1.55 (d, 1H, J=12.1 Hz), 1.27 (s,3H), 0.82 (t, 6H, J=6.4 Hz), 0.71 (d, 3H, J=6.9 Hz). MS (electrospray)M+1=455. Calculated=455.

N-{(2′S)-[3-(3-Methoxy-4-hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(17). Prepared from compound 6c and3-(3-methoxy-4-hydroxyphenyl)propionic acid according to the generalprocedure. Purity (87%); ¹H NMR (MeOH-d4) d 7.15 (t, 1H, J=7.7 Hz),6.81-6.76 (m, 3H), 6.67 (d, 3H, J=3.3 Hz), 3.98 (brm, 1H), 3.80 (s, 3H),2.86-2.69 (m, 3H), 2.53-2.22 (m, 8H), 1.89 (brs, 2H), 1.55 (d, 1H,J=12.0 Hz), 1.27 (s, 3H), 0.82 (dd, 6H, J=6.6, 3.2 Hz), 0.67 (d, 3H,J=6.9 Hz). MS (electrospray) M+1=469. Calculated=469.

N-{(2′S)-[3-(3-Methoxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(18). Prepared from compound 6e and 3-(3-methoxyphenyl)propionic acidaccording to the general procedure. Purity (88%); ¹H NMR (MeOH-d4) δ7.30-7.12 (m, 4H), 6.9-6.8 (m, 4H), 3.95 (brs, 1H), 3.76 (s, 3H), 2.96(d, 2H, J=6.8 Hz), 2.86-2.72 (m, 1H), 2.65-2.61 (m, 1H), 2.56-2.14 (m,7H), 1.91 (brs, 1H), 1.73-1.71 (m, 1H), 1.52 (d, 1H, J=13.0 Hz), 1.26(s, 3H), 0.81 (t, 6H, J=6.7 Hz), 0.67 (d, 3H, J=6.9 Hz). MS(electrospray) M+1=453. Calculated=453.

N-{2′-[3-(4-Hydroxyphenyl)propanamido]ethyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(19). Prepared from compound 6a and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (82%); ¹H NMR (MeOH-d4) δ7.13-6.99 (m, 3H), 6.79-6.67 (m, 4H), 6.59 (dd, 1H, J=7.3, 1.8 Hz),3.32-3.25 (m, 3H), 2.83-2.77 (m, 3H), 2.58 (s, 2H), 2.46-2.15 (m, 6H),1.98 (brs, 1H), 1.58 (brd, 1H, J=12.8 Hz), 1.29 (s, 3H), 0.76 (d, 3H,J=7.0 Hz). MS (electrospray) M+1=397. Calculated=397.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]propyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(20). Prepared from compound 6c and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (88%); ¹H NMR (MeOH-d4) δ7.77 (s, 1H), 7.08 (t, 1H. J=8.1 Hz), 6.98 (d, 2H, J=8.4 Hz), 6.74-6.67(m, 4H), 6.7 (d, 1H, J=7.5 Hz), 4.03 (dd, 1H, J=6.4 Hz), 2.81-2.70 (m,3H), 2.49 (s, 2H), 2.49 (s, 2H), 2.44-2.26 (m, 4H), 2.16 (td, 2H, J=3.7,10.9 Hz), 1.92-1.89 (m, 1H), 1.50 (d, 1H, J=12.3 Hz), 1.23 (s, 3H), 1.04(d, 3H, J=6.4 Hz), 0.71 (d, 3H, J=6.9 Hz). MS (electrospray) M+1=411.Calculated=411.

N-{2′-[3-(4-Hydroxyphenyl)-N-methylpropanamido]ethyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(21). Prepared from compound 6b and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (78%); ¹H NMR (MeOH-d4) δ7:84 (s, 1H), 7.18-7.00 (m, 3H), 6.77-6.69 (m, 4H), 6.60 (d, 1H, J=8.1Hz), 3.47-3.27 (m, 2H), 2.92-2.90 (m, 3H), 2.82-2.77 (m, 3H), 2.67-2.54(m, 3H), 2.47-2.18 (m, 3H), 1.96 (brs, 1H), 1.58-1.49 (m, 3H), 1.27 (d,3H, J=2.91 Hz), 0.73 (t, 3H, J=6.5 Hz). MS (electrospray) M+1=411.Calculated=411.

N-{(2′S)-[3-(4-Hydroxyphenyl)-N-methylpropanamido]propyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(22). Prepared from compound 6d and 3-(4-hydroxyphenyl)propionic acidaccording to the general procedure. Purity (89%); ¹H NMR (MeOH-d4) δ7.09 (t, 1H, J=7.9 Hz), 6.99 (d, 2H, J=8.2 Hz), 6.78-6.66 (m, 4H),6.58-6.56 (m, 1H), 4.92-4.86 (m, 1H), 2.74 (s, 3H), 2.27-2.17 (m, 2H),1.96-1.95 (brm, 1H), 1.55 (brd, 1H, J=14.3 Hz), 1.27 (s, 3H), 1.02 (d,3H, J=6.7 Hz), 0.66 (d, 3H, J=6.9 Hz). MS (electrospray) M+1=425.Calculated=425.

N-{(2′S)-[3-(4-Hydroxyphenyl)-N-methylpropanamido]-2′-phenylethyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(23). Prepared according to the general procedure using compound 6j and3-(4-hydroxyphenyl)propionic acid according to the general procedure.Purity (86%); ¹H NMR (MeOH-d4) δ 7.69-7.66 (m, 1H), 7.45-7.42 (m, 1H),7.32-6.97 (m, 7H), 6.76 (d, 1H, J=9.4 Hz), 6.73 (s, 1H), 6.66-6.64 (m,1H), 6.59-6.57 (m, 1H), 6.05 (q, 1H, J=5.5 Hz), 3.00-2.71 (m, 9H),2.65-2.63 (m, 2H), 2.29 (td, 1H, J=4.3, 8.4 Hz), 2.01-2.00 (brm, 1H),1.59 (brd, 1H, J=12.0 Hz), 1.32-1.28 (m, 6H), 0.71 (d, 3H, J=6.9 Hz). MS(electrospray) M+1=487. Calculated=487.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-4′-methylpentyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(24). Prepared according to the general coupling procedure (though on a3-mmol scale) using compound 6g and 3-(4-hydroxyphenyl)propionic acid in85% yield. Crude products were then purified by silica gelchromatography using 10-25% methanol in chloroform: ¹H NMR (MeOH-d4) δ7.85 (s, 1H), 7.26-7.06 (m, 6H), 6.97 (d, 2H, J=8.5 Hz), 6.76-6.66 (m,3H), 6.58 (d, 1H, J=7.2 Hz), 4.27 (t, 1H, J=7.3 Hz), 2.84-2.23 (m, 10H),1.93 (brd, 1H, J=7.2 Hz), 1.52 (d, 1H, J=12.0 Hz), 1.25 (s, 3H), 1.05(t, 1H, J=7.2 Hz), 0.74 (d, 3H, J=6.9 Hz); ¹³C NMR (MeOH-d4) δ 164.0,147.5, 143.0, 142.6, 129.0, 122.3, 119.9, 119.6, 119.3, 118.5, 116.5,107.3, 105.5, 103.0, 102.2, 51.6, 46.1, 40.8, 29.4, 29.3, 29.3, 28.7,21.4, 21.0, 17.3. Anal. (C₂₈H₄₀N₂O₃): C, H, N.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-methylpentyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(25). Prepared according to the general procedure (though on a 3-mmolscale) using compound 6h and 3-(4-hydroxyphenyl)propionic acid in 81%yield. Crude products were then purified by silica gel chromatographyusing 10-25% methanol in chloroform: ¹H NMR (MeOH-d4) δ 7.59 (s, 1H),6.90-6.76 (m, 3H), 6.52-6.45 (m, 3H), 6.36 (d, 1H, J=7.6 Hz), 3.89 (brs,1H), 2.56-2.54 (m, 3H), 2.39-1.95 (m, 9H), 1.70 (brs, 1H), 1.32-1.10 (m,3H), 1.03 (s, 5H), 0.65-0.61 (m, 8H), 0.52-0.42 (m, 3H); ¹³C NMR(MeOH-d4) δ 163.8, 147.5, 146.0, 142.6, 122.2, 119.7, 119.4, 107.4,105.5, 103.1, 102.6, 68.7, 53.7, 46.2, 41.0, 39.4, 39.1, 35.4, 33.4,29.5, 28.9, 28.7, 21.5, 21.2, 17.5, 15.1, 13.3, 11.9. Anal.(C₂₈H₄₀N₂O₃): C, H, N.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-2′-cyclohexylethyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine.(26). Prepared according to the general procedure (though on a 3-mmolscale) using compound 6i and 3-(4-hydroxyphenyl)propionic acid in 87%yield. Crude products were then purified by silica gel chromatographyusing 10-25% methanol in chloroform: ¹H NMR (MeOH-d4) δ 7.85-7.82 (m,2H), 7.11-6.97 (m, 3H), 6.74-6.56 (m, 5H), 3.99-3.97 (m, 1H), 2.81-2.75(m, 3H), 2.54 (m, 1H), 2.44-2.12 (m, 7H), 1.94 (brs, 1H), 1.54-1.26 (m,3H), 1.25 (s, 3H), 1.02-0.68 (m, 10H); ¹³C NMR (MeOH-d4) δ 164.1, 147.5,146.0, 142.6, 122.2, 119.7, 119.4, 107, 110.5, 1.03.1, 102.5, 68.7,49.4, 45.5, 41.3, 40.9, 29.4, 28.8, 28.4, 21.5, 21.1, 17.4, 15.4. Anal.(C₃₀H₂₄N₂O₃): C, H, N.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-phenylpropyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(27). Prepared according to the general procedure (though on a 3-mmolscale)using compound 6k and 3-(4-hydroxyphenyl)propionic acid in 82%yield. Crude products were then purified by silica gel chromatographyusing 10-25% methanol in chloroform: ¹H NMR (MeOH-d4) δ 7.88 (s, 1H),7.12-7.00 (m, 3H), 6.76-6.66 (m, 4H), 6.59-6.55 (m, 1H), 3.90 (m, 1H),2.78 (q, 3H, J=7.0 Hz), 2.62-2.56 (m, 1H), 2.47-2.24 (m, 6H), 1.66-1.50(m, 6H), 1.26 (s, 3H), 1.16-1.03 (m, 3H), 0.88-0.84 (m, 2H), 0.71 (d,3H, J=6.9 Hz); ¹³C NMR (MeOH-d4) δ 164.1, 147.5, 146.0, 142.6, 122.1,119.8, 119.4, 107.3, 105.5, 103.1, 102.6, 68.7, 50.1, 45.6, 41.2, 41.1,31.7, 29.4, 28.8, 21.5, 21.1, 20.3, 18.4, 17.4, 16.8. Anal.(C₃₁H₂₈N₂O₃): C, H, N.

Opioid Binding Assays. Mu binding sites were labeled using[³H][D-Ala²-MePhe⁴,Gly-ol⁵]enkephalin ([³H]DAMGO) (2.0 nM, SA=45.5Ci/mmol), and delta binding sites were labeled using[³H][D-Ala²,D-Leu⁵]enkephalin (2.0 nM, SA=47.5 Ci/mmol) using rat brainmembranes prepared as described.⁴ Kappa-1 binding sites were labeledusing [³H]U69,593 (2.0 nM, SA=45.5 Ci/mmol) and guinea pig membranespretreated with BIT and FIT to deplete the mu and delta binding sites.⁵

[³H]DAMGO binding proceeded as follows: 12×75 mm polystyrene test tubeswere prefilled with 100 μL of the test drug which was diluted in bindingbuffer (BB: 10 mM Tris-HCl, pH 7.4, containing 1 mg/mL BSA), followed by50 μL of BB, and 100 μL of [³H]DAMGO in a protease inhibitor cocktail(10 mM Tris-HCl, pH 7.4, which contained bacitracin (1 mg/mL), bestatin(100 μg/mL), leupeptin (40 μg/mL), and chymostatin (20 μg/mL).Incubations were initiated by the addition of 750 μL of the preparedmembrane preparation containing 0.2 mg/mL of protein and proceeded for 4to 6 h at 25° C. The ligand was displaced by 10 concentrations of testdrug, in triplicate, 2×. Nonspecific binding was determined using 20 μMlevallorphan. Under these conditions, the K_(d) of [³H]DAMGO binding was4.35 nM. Brandel cell harvesters were used to filter the samples overWhatman GF/B filters, which were presoaked in wash-buffer (ice-cold 10mM Tris-HCl, pH 7.4).

[³H][D-Ala²,D-Leu⁵]enkephalin binding proceeded as follows: 12×75 mmpolystyrene test tubes were prefilled with 100 μL of the test drug whichwas diluted in BB, followed by 100 μL of a salt solution containingcholine chloride (1 M, final concentration of 100 mM), MnCl2 (30 mM,final concentration of 3.0 mM), and, to block mu sites, DAMGO (1000 nM,final concentration of 100 nM), followed by 50 μL of[³H][D-Ala²,D-Leu⁵]enkephalin in the protease inhibitor cocktail.Incubations were initiated by the addition of 750 [L of the preparedmembrane preparation containing 0.41 mg/mL of protein and proceeded for4 to 6 h at 25° C. The ligand was displaced by 10 concentrations of testdrug, in triplicate, 2×. Nonspecific binding was determined using 20 μMlevallorphan. Under these conditions the K_(d) of[³H][D-Ala²,D-Leu⁵]enkephalin binding was 2.95 nM. Brandel cellharvesters were used to filter the samples over Whatman GF/B filters,which were presoaked in wash buffer (ice-cold 10 mM Tris-HCl, pH 7.4).

[³H]U69,593 binding proceeded as follows: 12×75 mm polystyrene testtubes were prefilled with 100 μL of the test drug which was diluted inBB, followed by 50 μL of BB, followed by 100 μL of [³H]U69,593 in thestandard protease inhibitor cocktail with the addition of captopril (1mg/mL in 0.1N acetic acid containing 10 mM 2-mercapto-ethanol to give afinal concentration of 1 μg/mL). Incubations were initiated by theaddition of 750 μL of the prepared membrane preparation containing 0.4mg/mL of protein and proceeded for 4 to 6 h at 25° C. The ligand wasdisplaced by 10 concentrations of test drug, in triplicate, 2×.Nonspecific binding was determined using 1 μM U69,593. Under theseconditions the K_(d) of [³H]U69,593 binding was 3.75 nM. Brandel cellharvesters were used to filter the samples over Whatman GF/B filters,which were presoaked in wash buffer (ice-cold 10 mM Tris-HCl, pH 7.4)containing 1% PEI.

For all three assays, the filtration step proceeded as follows: 4 mL ofthe wash buffer was added to the tubes, rapidly filtered and wasfollowed by two additional wash cycles. The tritium retained on thefilters was counted, after an overnight extraction into ICN Cytoscintcocktail, in a Taurus beta counter at 44% efficiency.

[³⁵S]-GTP-γ-S Binding Assay. Ten frozen guinea pig brains (HarlanBioproducts for Science, Inc, Indianapolis, Ind.) were thawed, and thecaudate putamen were dissected and homogenized in buffer A (3mL/caudate) (Buffer A=10 mM Tris-HCl, pH 7.4 at 4° C. containing 4 μg/mLleupeptin, 2 μg/mL chymostatin, 10 μg/mL bestatin, and 100 μg/mLbacitracin) using a polytron (Brinkman) at setting 6 until a uniformsuspension was achieved. The homogenate was centrifulged at 30,000×g for10 min at 4° C. and the supernatant discarded. The membrane pellets werewashed by resuspension and centrifugation twice more with fresh bufferA, aliquotted into microfuge tubes, and centrifuged in a Tomyrefrigerated microfuge (model MTX 150) at maximum speed for 10 min. Thesupernatants were discarded, and the pellets were stored at −80° C.until assayed.

For the [³⁵S]GTP-γ-S binding assay, all drug dilutions were made up inbuffer B [50 mM TRIS-HCl, pH 7.7/0.1% BSA]. Briefly, 12×75 mmpolystyrene test tubes received the following additions: (a) 50 μLbuffer B with or without an agonist, (b) 50 μL buffer B with or without60 μM GTP-γ-S for nonspecific binding, (c) 50 μL buffer B with orwithout an antagonist, (d) 50 μL salt solution which contained in bufferB 0.3 nM [³⁵S]GTP-γ-S, 600 mM NaCl, 600 μM GDP, 6 mM dithiothreitol, 30mM MgCl₂, and 6 mM EDTA, and (e) 100 μL membranes in buffer B to give afinal concentration of 10 μg per tube. The final concentration of thereagents were 100 mM NaCl, 5 mM MgCl₂, 1 mM EDTA, 1 mM dithiothreitol,100 μM GDP, 0.1% BSA, 0.05-0.1 nM [³⁵S]GTP-γ-S, 500 nM or 10 μMagonists, and varying concentrations (at least 10 differentconcentrations) of antagonists. The reaction was initiated by theaddition of membranes and terminated after 4 h by addition of 3 mLice-cold (4° C.) purified water (Milli-Q uv-Plus, Millipore) followed byrapid vacuum filtration through Whatman GF/B filters presoaked inpurified water. The filters were then washed once with 5 mL ice-coldwater. Bound radioactivity was counted by liquid scintillationspectroscopy using a Taurus (Micromedic) liquid scintillation counter at98% efficiency after an overnight extraction in 5 mL Cytoscintscintillation fluid. Nonspecific binding was determined in the presenceof 10 μM GTP-γ-S. Assays were performed in triplicate, and eachexperiment was performed at least 3×.

Data Analysis. The data of the two separate experiments (opioid bindingassays) or three experiments ([³⁵S]-GTP-γ-S assay) were pooled and fit,using the nonlinear least-squares curve-fitting language MLAB-PC(Civilized Software, Bethesda, Md.), to the two-parameter logisticequation⁶ for the best-fit estimates of the IC₅₀ and slope factor. TheK_(i) values were then determined using the equation: IC₅₀/1+([L]K_(d)).

% Inhibition Data for Compounds of Formula (I) in a Kappa Receptor Assay

R₁ R₂ R₃ (acid) % Inhibition H H PA5 13 H H BA1 20 H H BA2 20 H H BA4 21H H BA6 32 H H BA8 11 H H BA9 24 H H BA10 28 H H BA12 6 H H BA13 9 H HBA14 11 H H BA16 11 H H BA22 2 H H BA23 13 H H BA24 2 H H BA25 6 H H AA21 H H AA4 0 H H PP1 9 H H PP2 23 H H PP3 17 H H PP4 1 H H PP5 8 H H PP614 H H PP12 29 H H PP15 19 H H FA1 13 H H FA2 9 H H FA3 50 H H FA4 33 HH FA5 39 H H FA6 27 H H FA7 29 H H FA8 35 H H FA9 33 H H FA10 8 H H HA120 H H HA2 42 H H HA3 9 H H HA4 15 H H HA5 20 H H OA23 8 H H PB1 37 H HCA2 35 H H CA10 23 H H CA11 13 H H CA12 15 H H PA38 14 H H CA19 10 H HCA20 12 H H CA22 19 H H CA38 27 H H PA9 18 H H PA10 9 H H PA13 25 H HPA15 17 H H PA18 16 H H PA23 9 H H PA27 18 H H PA28 9 H H PA29 10 H HPA32 22 H H PA3 20 H H PA4 11 H H PA7 9 H H PA17 13 H H PA22 19 H H PA823 H H NA1 16 H H NA2 6 H H NA3 13 H H NA4 1 H H NA5 10 H H NA6 2 H HNA7 2 H H NA8 15 H H NA9 26 H H NA10 22 H H NA11 15 H H BA7 2 H H PA38 5H H AA1 8 H H AA2 6 H H AA4 3 H H PP6 11 H CH₃ BA4 12 H CH₃ BA10 13 HCH₃ BA1 6 H CH₃ CA1 9 H CH₃ CA5 6 H CH₃ PA37 5 H CH₃ PA5 11 H CH₃ PA14 0H CH₃ PA32 0 H CH₃ PP2 0 H CH₃ PP5 0 H CH₃ PP6 0 H CH₃ PP1 0 H CH₃ PP7 0H CH₃ BA11 0 H CH₃ CA4 0 αi-Pr H BA4 9 αi-Pr H BA5 19 αi-Pr H BA8 0αi-Pr H BA7 5 αi-Pr H BA11 0 αi-Pr H BA12 0 αi-Pr H BA13 26 αi-Pr H BA151 αi-Pr H BA19 0 αi-Pr H BA20 0 αi-Pr H BA21 3 αi-Pr H CA1 0 αi-Pr HCA10 0 αi-Pr H CA11 0 αi-Pr H CA7 0 αi-Pr H PA5 6 αi-Pr H PA7 14 αi-Pr HPA9 0 αi-Pr H PA10 0 αi-Pr H PA13 10 αi-Pr H PA15 4 αi-Pr H PA18 7 αi-PrH PA22 0 αi-Pr H PA27 18 αi-Pr H PA28 6 αi-Pr H CA16 0 αi-Pr H CA18 0αi-Pr H PA29 1 αi-Pr H PP1 28 αi-Pr H PP2 3 αi-Pr H PP3 27 αi-Pr H PP418 αi-Pr H PP5 20 αi-Pr H PP6 70 αi-Pr H PP7 13 αi-Pr H PP8 17 αi-Pr HPP12 23 αi-Pr H PP15 26 αi-Pr H PP16 31 αi-Pr H PP17 43 αi-Pr H CA5 4αi-Pr H CA7 16 αi-Pr H CA12 15 αi-Pr H PA8 21 αi-Pr H PA23 6 αi-Pr HPA32 13 αi-Pr H BA1 3 αi-Pr H CA4 3 αi-Pr H PA18 7 αi-Pr H NA1 14 αi-PrH NA2 3 αi-Pr H NA3 16 αi-Pr H NA4 43 αi-Pr H NA5 61 αi-Pr H NA6 1 αi-PrH NA7 22 αi-Pr H NA8 3 αi-Pr H NA9 33 αi-Pr H NA10 3 αi-Pr H NA11 34αi-Pr H BA7 25 αi-Pr H PA38 4 αi-Pr H AA1 3 αi-Pr H AA2 4 αi-Pr H AA4 13αi-Pr H CA2 5 αi-Pr H FA1 5 αi-Pr H FA2 6 αi-Pr H FA3 9 αi-Pr H FA4 17αi-Pr H FA5 10 αi-Pr H FA6 10 αi-Pr H FA7 10 αi-Pr H FA8 27 αi-Pr H FA914 αi-Pr H FA10 6 αi-Pr H HA1 6 αi-Pr H HA2 1 αi-Pr H HA3 0 αi-Pr H HA410 αi-Pr H HA5 10 αi-Pr H OA23 0 αi-Pr H PB1 7 αi-Pr H PA14 8 βi-Pr HPP4 52 βi-Pr H PP6 11 βi-Pr H PP8 10 βi-Pr H PP12 50 βi-Pr H PP15 24βi-Pr H PP16 8 βi-Pr H PP17 10 βi-Pr H PP18 5 αCH₃ H PP6 11 αCH₃ CH₃ CA13 αCH₃ CH₃ CA2 0 αCH₃ CH₃ CA8 0 αCH₃ CH₃ CA14 0 αCH₃ CH₃ CA15 1 αCH₃ CH₃CA19 0 αCH₃ CH₃ CA20 10 αCH₃ CH₃ CA24 5 αCH₃ CH₃ CA28 0 αCH₃ CH₃ CA30 7αCH₃ CH₃ BA1 7 αCH₃ CH₃ BA4 7 αCH₃ CH₃ BA8 8 αCH₃ CH₃ BA13 8 αCH₃ CH₃BA19 8 αCH₃ CH₃ BA20 5 αCH₃ CH₃ BA21 5 αCH₃ CH₃ BA23 6 αCH₃ CH₃ BA25 5αCH₃ CH₃ PA5 6 αCH₃ CH₃ PA8 1 αCH₃ CH₃ PA10 0 αCH₃ CH₃ PA19 0 αCH₃ CH₃PA21 0 αCH₃ CH₃ PA27 4 αCH₃ CH₃ PA28 0 αCH₃ CH₃ PA29 1 αCH₃ CH₃ PA32 0αCH₃ CH₃ PA14 0 αCH₃ CH₃ PP1 6 αCH₃ CH₃ PP4 2 αCH₃ CH₃ PP5 3 αCH₃ CH₃PP7 1 αCH₃ CH₃ PP8 0 αCH₃ CH₃ PP10 5 αCH₃ CH₃ BAL1 0 αCH₃ CH₃ GAB1 0αCH₃ CH₃ INP1 0 αCH₃ CH₃ CA13 1 αCH₃ CH₃ PA17 0 αCH₃ CH₃ PA9 10 αCH₃ CH₃BA24 2 αCH₃ CH₃ PP2 5 αCH₃ CH₃ PP3 1 αCH₃ CH₃ PP6 1 αCH₃ CH₃ PA20 4 αPhCH₃ CA1 0 αPh CH₃ CA4 0 αPh CH₃ CA9 1 αPh CH₃ CA14 0 αPh CH₃ CA15 3 αPhCH₃ CA19 0 αPh CH₃ CA20 2 αPh CH₃ BA1 3 αPh CH₃ BA2 0 αPh CH₃ BA4 0 αPhCH₃ PA14 3 αPh CH₃ PA19 0 αPh CH₃ PP1 4 αPh CH₃ PP2 4 αPh CH₃ OA1 9 αPhCH₃ OA3 4 αPh CH₃ CA2 5 αPh CH₃ BA21 7 αPh CH₃ PP3 5 αPh CH₃ GAB1 11 αPhCH₃ BA8 4 αPh CH₃ BA10 0 αPh CH₃ BA15 15 αPh CH₃ PA8 1 αPh CH₃ PA9 0 αPhCH₃ PA10 6 αPh CH₃ PA20 6 αPh CH₃ PA21 9 αPh CH₃ PP6 7 αPh CH₃ PP7 0 αPhCH₃ PP8 0 αPh CH₃ OA2 0 Amino Alkyl Acids AA 1 1-Piperidine PropionicAcid 157.21 AA 2 2-N,N-Dimethyl Glycine 103.21 AA 3 3-N,N-Dimethyl AminoPropionic Acid AA 4 4-N,N-Dimethyl Amino Butyric Acid 167.64 BenzoicAcids BA 1 Benzoic Acid 122.12 BA 2 2-Chlorobenzoic Acid 156.57 BA 32-Acetamidobenzoic Acid 179.18 BA 4 2-Phenoxybenzoic Acid 214.22 BA 63-Chlorobenzoic Acid 156.57 BA 8 3-Phenoxybenzoic Acid 214.22 BA 93-Hydroxybenzoic Acid 138.12 BA 10 4-Chlorobenzoic Acid 156.57 BA 74-Dimethylaminobenzoic Acid 165.19 BA 12 4-Dodecyloxybenzoic Acid 306.45BA 13 4-Butoxybenzoic Acid 212.69 BA 14 4-Hydroxybenzoic Acid 138.12 BA16 4-tert-butylbenzoic Acid 178.23 BA 18 4-Acetamidobenzoic Acid 179.18BA 19 o-Anisic Acid 152.15 BA 20 m-Anisic Acid 152.15 BA 21 p-AnisicAcid 152.15 BA 22 2-Benzoylbenoic Acid 226.23 BA 23 2-BiphenylbenzoicAcid 98.22 BA 24 4-Biphenylbenzoic Acid 98.22 BA 253-Dimethylaminobenzoic Acid 165.19 BA 26 2-Fluorobenzoic Acid 140.11 BA27 3-Nitrobenzoic Acid 167.12 BA 28 o-Tolylic Acid 136.15 BA 29m-Tolylic Acid 136.15 BA 30 p-Tolylic Acid 136.15 BA 314-Fluoro-3-nitrobenzoic 185.11 BA 32 3,4-Dichlorobenzoic Acid 191.01 BA33 2-Hydroxy Benzoic acid 138.12 BA 34 4-Chloro-3-Nitro Benzoic Acid201.57 BA 35 4-Fluorobenzoic Acid 140.11 BA 36 2-Nitrobenzoic acid167.12 BA 37 4-Nitrobenzoic acid 167.12 Cinnamic Acids CA 1a-Methylcinnamic Acid 162.19 CA 2 a-Phenylcinnamic Acid 226.4 CA 32-Bromo-4,5-dimethoxycinnamic Acid 287.11 CA 4 2-Chlorocinnamic Acid182.61 CA 5 2,4-Dichlorocinnamic Acid 217.05 CA 6 3,4-DihydroxycinnamicAcid 180.16 CA 7 2,4-Dimethoxycinnamic Acid 208.21 CA 83,5-Di-tert-butyl-4-hydroxycinnamic Acid 276.37 CA 9 3-FluorocinnamicAcid 166.15 CA 10 2-Hydroxycinnamic Acid 164.16 CA 11 3-HydroxycinnamicAcid 164.16 CA 12 4-Hydroxycinnamic Acid 164.16 CA 13 2-MethoxycinnamicAcid 178.19 CA 14 3-Methoxycinnamic Acid 178.19 CA 15 4-MethoxycinnamicAcid 178.19 CA 16 2-Methylcinnamic Acid 162.19 CA 17 3-MethylcinnamicAcid 162.19 CA 18 4-Methylcinnamic Acid 162.19 CA 193-(1-Naphthyl)acrylic Acid 224.46 CA 20 4-Phenylcinnamic Acid 224.26 CA21 3,4,5-Trimethoxycinnamic Acid 238.24 CA 22 4-Isopropylcinnamic acid190.24 CA23 2,6-Dichloro 218.063 CA24 3-benzyloxy 254.234 CA252-bromo-4,5-dimethoxy 287.12 CA26 2-chloro-6-fluoro 200.6 CA27alpha-methyl-2,4,5-trimethoxy 252.27 CA28 2-n-hexyloxy 250.22 CA295-bromo-2-methoxy 257.09 CA30 2-benzyloxy 254.234 CA31 2,4,5-trimethoxy238.24 CA32 2,6-difluoro 184.14 CA33 2-t-butylthio 236.157 CA342-chloro-5-nitro 227.61 CA35 2,3-dimethoxy 208.21 CA363,5-dit-butyl-4-hydroxy 276.37 CA37 2,5-dimethoxy 208.22 CA 38trans-Cinnamic Acid 147 CA39 cis-Cinnamic Acid 147 Fatty Acids FA 1Acetic Acid 60.05 FA 2 Propionic Acid 74.08 FA 3 Pivalic Acid 102.13 FA4 1-Phenyl-1-cyclopentane Acid 162.19 FA 5 1-Phenyl-1-cyclopropane Acid190.24 FA 6 Isovaleric Acid 102.13 FA 7 4-Methylvaleric Acid 116.16 FA 8Cyclopentylacetic Acid 128.17 FA 9 Cyclopentylcarboxylic Acid 114.14 FA10 trans-2-Phenyl-1-cyclopropyl CA 162.19 FA 11 Cyclohexane carboxylicAcd 128.17 Hydroxy Acids HA 1 2-Hydroxy-3-methyl butyric 118.13 HA 22-Hydroxy-2-methyl butyric 118.13 HA 3 3-Hydroxy butyric 104.11 HA 43-Hydroxy-4-trimethylamino butyric 197.66 HA 5 2-Phenyl-3-hydroxypropionic 166.18 Nicotinic Acids NA 1 2(n-Amylthio)nicotinic Acid 225.31NA 2 5-Bromonicotinic Acid 202.01 NA 3 6-Chloronicotinic Acid 157.56 NA4 2-Chloronicotinic Acid 157.56 NA 5 2-(Methylthio)nicotinic Acid 169.2NA 6 Nicotinic Acid 123.11 NA 7 Picolinic Acid 123.11 NA 82-Pyridylacetic Acid HCl 173.6 NA 9 3-Pyridylacetic Acid HCl 173.6 NA 104-Pyridylacetic Acid HCl 173.6 NA 11 2-(Phenylthio)Nicotinic Acid 231.27NA 12 2-Hydroxy-6-methyl Nicotinic 153.14 NA13 3-(3-pyridyl)acrylic acid149.15 NA 14 3-(4-pyridyl)acrylic acid 149.15 Propionic Acid PP1 PhenylPropionic 150.18 PP2 3,3-Diphenylpropionic Acid 226.28 PP33-Phenylbutyric Acid 164.2 PP4 3-(2-Hydroxyphenyl)propionic Acid 166.18PP 5 3-(3-Hydroxyphenyl)propionic Acid 166.18 PP 63-(4-Hydroxyphenyl)propionic Acid 166.18 PP73-(3-Methoxyphenyl)propionic Acid 180.2 PP8 3-(4-Methoxyphenyl)propionicAcid 180.2 PP9 3-(3,4,5-Trimethoxyphenyl)propionic Acid 240.26 PP103-(2-Methoxyphenyl)propionic Acid 180.2 PP113-(2,5-Dimethoxyphenyl)propionic Acid 210.24 PP123-(2-Chlorophenyl)propionic Acid 184.62 PP13 3-(4-Aminophenyl)propionicAcid 165.119 PP14 3-(4-Fluorophenyl)propionic Acid 168.17 PP153-(3,4-Dihydroxyphenyl)propionic Acid 182.18 PP163-(3-Methoxy-4-hydroxyphenyl) 196.2 PP17 3-(3,5-dinotro-4-hydroxyphenyl)256.2 PP18 3-(Pentaflurophenyl)propionic Acid PP193-(4-Bocaminophenyl)propionic Acid 265 PP21 2,2-Diphenylpropionic Acid226.28 Phenylacetic Acid PA 1 4-Aminophenylacetic Acid 151.17 PA 24-Biphenylacetic Acid 288.55 PA 3 2-Bromophenylacetic Acid 215.05 PA 44-Bromophenylacetic Acid 215.05 PA 5 4-(n-Butoxy)phenylacetic Acid208.26 PA 7 3-Chloro-4-hydroxyphenylacetic Acid 186.59 PA 82-Chlorophenylacetic Acid 170.6 PA 9 3-Chlorophenylacetic Acid 170.6 PA10 4-Chlorophenylacetic Acid 170.6 PA 11 2-Chloro-6-fluorophenylaceticAcid 188.59 PA 12 2,4-Dichlorophenylacetic Acid 205.04 PA 132,6-Dichlorophenylacetic Acid 205.04 PA 14 3,4-Dichlorophenylacetic Acid205.04 PA 15 2,5-Dimethoxyphenylacetic Acid 196.2 PA 163,4-Dimethoxyphenylacetic Acid 196.2 PA 17 2,5-Dimethylphenylacetic Acid164.2 PA 18 2,4-Dinitrophenylacetic Acid 226.15 PA 192-Fluorophenylacetic Acid 154.14 PA 20 3-Fluorophenylacetic Acid 154.14PA 21 4-Fluorophenylacetic Acid 154.14 PA 22 2-Hydroxyphenylacetic Acid152.15 PA 23 4-Hydroxyphenylacetic Acid 152.15 PA 242-Methoxyphenylacetic Acid 166.18 PA 25 3-Methoxyphenylacetic Acid166.18 PA 26 4-Methoxyphenylacetic Acid 166.18 PA 272-Methylphenylacetic Acid 150.18 PA 28 3-Methylphenylacetic Acid 150.18PA 29 4-Methylphenylacetic Acid 150.18 PA 30 2-Nitrophenylacetic Acid181.15 PA 31 4-Nitrophenylacetic Acid 181.15 PA 32 Phenylacetic Acid136.15 PA 33 2-Trifluoromethylophenylacetic Acid 204.15 PA 343-Trifluoromethylphenylacetic Acid 204.15 PA 353,4,5-Trimethoxyphenylacetic Acid 226.23 PA 36 4-Ethoxyphenylacetic Acid180.22 PA 37 Mesitylacetic acid 178.23 PA 38 4-Dimethyl Amino PA PA 393-Hydroxyphenyl PA PA 40 Diphenyl Acetic

References

(1) Thomas, J. B.; Mascarella, S. W.; Rothman, R. B.; Partilla, J. S.;Xu, H.; McCullough, K. B.; Dersch, C. M.; Cantrell, B. E.; Zimmerman, D.M.; Carroll, F. I. Investigation of the N-substituent conformationgoverning potency and μ receptor subtype-selectivity in(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonists.J. Med. Chem. 1998, 41(11), 1980-1990.

(2) Mitch, C. H.; Leander, J. D.; Mendelsohn, L. G.; Shaw, W. N.; Wong,D. T.; Cantrell, B. E.; Johnson, B. G.; Reel, J. K.; Snoddy, J. D.;Takemori, A. E.; Zimmerman, D. M.3,4-Dimethyl-4-(3-hydroxyphenyl)piperidines: Opioid antagonists withpotent anorectant activity. J. Med. Chem. 1993, 36(20), 2842-2850.

(3) Xu, H.; Lu, Y.-F.; Partilla, J. S.; Brine, G. A.; Carroll, F. I.;Rice, K. C.; Lai, J.; Porreca, F.; Rothman, R. B. Opioid peptidereceptor studies. 6. The 3-methylfentanyl congeners RTI-4614-4 and itsenantiomers differ in efficacy, potency, and intrinsic efficacy asmeasured by stimulation of [³⁵S]GTP-γ-S binding using cloned μ-opioidreceptors. Analgesia 1997, 3, 3542.

(4) Rothman, R. B.; Xu, H.; Seggel, M.; Jacobson, A. E.; Rice, K. C.;Brine, G. A.; Carroll, F. I. RTI-4614-4: an analog of(+)-cis-3-methylfentanyl with a 27,000-fold binding selectivity for muversus delta opioid binding sites. Life Sci. 1991, 48, PL111-PL-116.

(5) Rothman, R. B.; Bykov, V.; de Costa, B. R.; Jacobson, A. E.; Rice,K. C.; Brady, L. S. Interaction of endogenous opioid peptides and otherdrugs with four kappa opioid binding sites in guinea pig brain. Peptides1990, 11, 311-331.

(6) Rodbard, D.; Lenox, R. H.; Wray, H. L.; Ramseth, D. Statisticalcharacterization of the random errors in the radioimmunoassaydose-response variable. Clin. Chem. 1976, 22, 350-58.

(7) Takemori et al, J. Pharm. Exp. Ther., 1988, 246 (1), 255-258.

TABLE 1 Results of Inhibition Screening of Selected Structural Isomersof Compound 8 Taken from the Library versus Kappa Opioid SelectiveLigand [³H]U69,593

% Inhibition compd R1 R2 X1 X2 S₁ S₂ S₃ at 100 nm  8 i-Pr H CH2 CH2 H HOH 71  9 i-Pr^(a) H CH2 CH2 H H OH 11 10 i-Pr H CH2 CH2 H H H 28 11 i-PrH CH2 CH2 H OH H 20 12 i-Pr H CH2 CH2 OH H H 25 13 i-Pr H CH2 — H H OH 614 i-Pr H CH^(b) CH^(b) H H OH 15 15 i-Pr H CH2 CH2 H H F 26 16 i-Pr HCH2 CH2 H OH OH 31 17 i-Pr H CH2 CH2 H OCH3 OH 42 18 i-Pr H CH2 CH2 H HOCH3 16 19 H H CH2 CH2 H H OH 11 20 CH₃ H CH2 CH2 H H OH 20 21 H CH₃ CH2CH2 H H OH 0 22 CH₃ CH₃ CH2 CH2 H H OH 1 23 C₆H₅ CH₃ CH2 CH2 H H OH 7DMSO 4 ^(a)The carbon to which the i-Pr group is attached has theopposite stereochemistry from that in 8. ^(b)Trans double bond

TABLE 2 Radioligand Binding Data for 8 and Related Compounds at Mu,Delta, and Kappa Opioid Receptor Assays

Ki(nM ± SD) (-n_(H)) compd R [³H]DAMGO [³H]DADLE [³H]U69, 593 μ/κ δ/κ 8i-Pr 393 ± 13.3 >5700 6.91 ± 0.55 57 >824 (0.89 ± 0.02) (0.81 ± 0.05) 24i-Bu 398 ± 72.3 NA 89.3 ± 7.03 4.5 (0.91 ± 0.16) (0.78 ± 0.05) 25 sec-Bu421 ± 30.5 NA 8.84 ± 0.30 47 (0.91 ± 0.06) (0.87 ± 0.02) 26 c-Hex 234 ±25.2 NA 83.1 ± 5.7 2.8 (0.84 ± 0.08) (0.79 ± 0.04) 27 Benzyl 9.6 ± 1.18NA 54.6 ± 3.5 0.17 (0.89 ± 0.09) (0.86 ± 0.04) 5a^(α) 0.74 ± 0.05 322 ±38.1 122 ± 11.9 0.006 2.6 (0.89 ± 0.09) (0.75 ± 0.09) (0.52 ± 0.07) 1(nor- 47.2 ± 3.3 42.9 ± 11 0.28 ± 0.07 181 150 BNI)^(b,c) naltrexone^(b)1.39 ± 0.40 94.9 ± 6.6 4.71 ± 0.12 0.30 20.1 (0.94 ± 0.08) (1.01 ± 0.09)(1.05 ± 0.08) ^(a)Data taken from ref. 1. ^(b)Data provided forreference; compound is not a derivative of 8. ^(c)Data taken from ref.7. [³H]DAMGO, [³H]DPDPE, and [³H]U69593 were used as the radioligandsfor the mu, delta, and kappa assays, respectively. Guinea pig brainmembranes were used.

TABLE 3 Inhibition by Antagonists of [³⁵S]GTPγS Binding in Guinea PigCaudate Stimulated by DAMGO (μ), SNC80 (δ), and U69,593 (κ) SelectiveOpioid Agonists. Ki (nM ± SD) (−n_(H))^(a) Compd DAMGO^(b) SNC80^(c)U69,593^(d) 8 7.25 ± 0.52  450 ± 74.1 4.70 ± 0.56 (1.11 ± 0.08) (1.05 ±0.17) (1.38 ± 0.19) 5a^(e) 0.039 ± 0.003  1.48 ± 0.094  1.04 ± 0.061(1.06 ± 0.07) (1.19 ± 0.08) (1.07 ± 0.06) 1, nor-BNI 16.75 ± 1.47  10.14± 0.96  0.038 ± 0.005 (1.02 ± 0.09) (1.18 ± 0.12) (0.97 ± 0.12)naltrexone 0.93 ± 0.21 19.3 ± 2.25 2.05 ± 0.21 (1.03 ± 0.22) (1.05 ±0.17) (1.38 ± 0.19) ^(a)See footnote a from Table 2. ^(b)DAMGO[(D-Ala²,MePhe⁴,Gly-ol⁵)enkephalin]. Agonist selective for mu opioidreceptor. ^(c)SNC-80([(+)-4-[(αR)-α-(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide).Agonist selective for delta opioid receptor. ^(d)U69,593[(5α,7α,8β-(−)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec- #8-yl]benzeneacetamide]. Agonist selective for kappa opioid receptor.^(e)Data taken from ref. 1.

Analyses Appendix

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-methylbutyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(8).

Anal. calcd for C₂₇H₃₉ClN₂O₃.1.5H₂O: C, 64.59, H, 8.43; N, 5.58. Found:64.35; H, 8.12; N, 5.38.

N-{(2′S)-(3-(4-Hydroxyphenyl)propanamido]-4′-methylpentyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(24).

Anal. calcd for C₂₈H₄₀N₂O₃: C, 74.30, H, 8.91; N, 6.19. Found: C, 74.12;H, 9.22; N, 6.30.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-methylpentyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(25).

Anal. calcd for C₂₈H₄₀N₂O₃: C, 74.30, H, 8.91; N, 6.19. Found: C, 74.02;H, 9.20; N, 6.25.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-2′-cyclohexylethyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(26).

Anal. calcd for C₃₀H₄₂N₂O₃: C, 75.28, H, 8.84; N, 5.85. Found: C, 75.18;H, 8.96; N, 5.97.

N-{(2′S)-[3-(4-Hydroxyphenyl)propanamido]-3′-phenylpropyl}-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine(27).

Anal. calcd for C₃₁H₃₈N₂O₃: C, 76.51, H, 7.87; N, 5.76. Found: C, 76.15;H, 7.99; N, 5.89.

Example 2 N-Substituted(±)-1,2,3,4,4a,5,10,10a-Octahydro-4a-(3-hydroxyphenyl)-10a-methylbenzo[g]isoquinolines

Summary

Potent, opioid receptor pure antagonist activity has been demonstratedin the N-substituted(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-10a-methylbenzo[g]isoquinolines,7 and 8 (FIG. 8). These compounds share many of the characteristicsidentified with the phenylpiperidine antagonists includingN-susbstituent mediated potency and a lack of N-susbstituent mediatedantagonism. Also, like the phenylpiperidines, 7 and 8 display a strongpreference for mu and kappa versus delta opioid receptor binding. Unlikethe phenylpiperidines however, the benzoisoquinoline system displays astronger preference for the kappa versus the mu opioid receptor and alower overall potency relative to typicaltrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine antagonists. Togetherthis data suggests a common site of action within the opioid receptorsfor compounds 7 and 8 and thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidines.

Chemistry

The N-methyl and N-phenethyl derivatives of(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-10a-methylbenzo[g]isoquinoline(7 and 8, respectively) were prepared starting from tetrahydropyridine(9) according to the method illustrated in FIG. 8.¹ Accordingly, 9 wasdeprotonated with sec-butyl lithium followed by alkylation withα,α′-dichloroxylene. This material was not isolated but was immediatelycyclized with NaI in refluxing acetonitrile and reduced with sodiumborohydride to provide intermediate 10 in 23% yield. The N-methylderivative (7) was then available via O-demethylation employingrefluxing HBr in acetic acid. The N-phenylethyl derivative (8) wasprepared from 10 by N-demethylation using phenylchloroformate inrefluxing toluene followed by subjecting the crude carbamate torefluxing HBr in acetic acid to cleave the urethane and deprotect thephenol. Conversion of this material to the desired compound (8) wasaccomplished by coupling with phenyl acetic acid usingbenzotriazol-1-yl-oxy-tris-(dimethylamino)phosphoniumhexafluorophosphate (BOP reagent) followed by reduction of the resultingamides using borane in tetrahydrofuran in 2.2% overall yield.

Results and Discussion

Both initial studies and work conducted in this laboratory have providedstrong evidence that the antagonist activity of some N-substitutedpiperidine compounds is expressed via a phenyl equatorial/piperidinechair receptor-ligand interaction as illustrated in FIG. 9b. ² Thisstands in contrast to the phenylaxial/piperidine chair conformationexhibited by naltrexone (FIG. 9a). The benzoisoquinoline system (FIG.9c), where a bridge connects carbons 3 and 4 in the piperidine ring, wasselected for study because its structure could potentially maintain theproposed active conformation of the phenylpiperdines as well as providesites for further structural elaboration. Compounds 7 and 8 weretherefore synthesized and tested in both binding and functional assaysto establish the overall effect of this structural change on antagonistactivity and potency.

The radioligand binding data for the N-methyl and N-phenethylderivatives of(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-10a-methylbenzo[g]isoquinolines(7 and 8, respectively) are provided in Table 4. For comparison, theradioligand binding assay data for the parent ligands 5 and 6 are givenin Table 5. As these data sets are from different assays, the bindingdata obtained for naltrexone (3) is provided as a reference standardfrom both sets of assays. Inspection of the data reveals a fundamentalshift in the receptor binding preference of the benzoisoquinolines infavor of the kappa receptor relative to the phenylpiperidines whichtypically show greater potency at the mu receptor. However, the overallpreference for mu/kappa binding relative to delta binding is preserved(the phenylpiperidines typically show the least preference for the deltareceptor, data not shown). Increasing the size of the N-substituent(conversion of 7 to 8) provides an overall increase in potency at allreceptors, a feature shared by conversion of the phenylpiperidine 5 to6. The latter information together with the general receptor bindingpreferences suggests that the benzoisoquinoline antagonists probablyinteract with the same subsites within the opioid receptors as do thephenylpiperidines, but the addition of the 3,4 bridge leads to both anincrease in affinity for the kappa receptor as well as a loss ofaffinity for the mu receptor relative to the phenylpiperidineantagonists.

In the functional assay shown in Table 6, compounds 7 and 8 displayed apattern of activity consistent with the radioligand binding assay. Thus,inhibition of agonist stimulated [³⁵S]GTPγS binding in guinea pigcaudate by 7 and 8, a measure of functional antagonist activity,⁴ wasgreatest against U69,593 (kappa receptor) with the potency demonstratedagainst DAMGO (mu receptor) being only slightly less. The ability toinhibit SNC80 (delta receptor) stimulated [³⁵S]GTPγS binding wassignificantly lower. As in the previous assay, increasing the size ofthe N-substituent lead to an increase in potency. Importantly, neitherthe N-methyl derivative 7 nor the N-phenethyl derivative 8 stimulated[³⁵S]GTPγS binding when tested at concentrations as high as 1 μM; thebenzoisoquinoline structure therefore retains opioid pure antagonistactivity.

In terms of potency, both 7 and 8 demonstrate a decreased affinity forall of the opioid receptors relative to some of the more potentphenylpiperidine antagonists. The source of this loss of activity cannotbe immediately established since several explanations exist. It ispossible that these compounds have greater preference for a phenylaxial/piperidine chair conformation relative to the phenylpiperidines,though it has been found that 8 exists in thephenylequatorial/piperidine chair conformation in the solid state (FIG.10). More likely, the lower potency results from a lack of activity ofone of the enantiomers of 6. Hugh eudismic ratios are observed in mostclasses of opioid ligands.

In summary, potent opioid receptor pure antagonist activity wasdemonstrated for(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-2-phenethyl-10a-methylbenzo[g]isoquinoline(8). Compounds 7 and 8 share many of the characteristics identified withthe phenylpiperidine antagonists including N-substituent mediatedpotency and a lack of N-substituent mediated antagonism. Also, theseligands display a strong preference for mu and kappa versus deltabinding. Unlike the phenylpiperidines, the benzoisoquinolines display astronger preference for the kappa versus the mu receptor and a loweroverall potency as, a racemic mixture, relative to typicaltrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine antagonists. Togetherthis data suggests both a common site of action within the opioidreceptors for compounds, 7 and 8 and thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidines.

Experimental

Melting points were determined on a Thomas-Hoover capillary tubeapparatus and are not corrected. Elemental analyses were obtained byAtlantic Microlabs, Inc. and are within ±0.4% of the calculated values.¹H and ¹³C NMR were determined on a Bruker WM-250 spectrometer usingtetramethylsilane as an internal standard. Radial chromatography wasperformed on a Harrison Research Chromatotron model 7924T. All reactionswere followed by thin-layer chromatography using Whatman silica gel 60TLC plates and were visualized by UV or by charring using 5%phosphomolybdic acid in ethanol. All solvents were reagent grade.Tetrahydrofuran and diethyl ether were dried over sodium benzophenoneketyl and distilled prior to use. α,α′-Dichloroxylene, purchased fromAldrich Chemical Co., was recrystallized from hexane prior to use.

(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-methoxyphenyl)-2,10a-dimethylbenzo-[g]isoquinoline(10): To a dry three-neck round-bottomed flask was charged 500 mg (2.3mmol) of tetrahydropyridine (9) (CAUTION: read reference 12 andreferences cited therein) and 20 mL dry THF. This was cooled to −78° C.,and to this was added 2.4 mL (3.12 mmol) s-BuLi (1.3M in cyclohexane)via a syringe over 5 min. The flask was then warmed to −0° C. and agedfor 10 min. The flask was then cooled to −78° C. and cannulated into amixture of 40 mL dry ethyl ether and 1.3 g (7.59 mmol) α,α-dichloroxylene at −50° C. over 20 min. This was aged for 20 min and thenquenched with ice-cold 1N HCl. The contents of the flask were thentransferred to a separatory funnel with ice-cold ether and ice. cold 1NHCl. The aqueous layer was removed and stored in an ice bath while theorganic layer was twice extracted with ice-cold 1N HCl. The combinedaqueous layers were placed into a new separatory funnel and extractedtwice with ice-cold ethyl ether to remove α,α′-diochloroxylene. Theaqueous layer was then made basic with 50% NaOH at first and finallysaturated NaHCO₃ to pH 10. The aqueous layer was then extracted 3 timeswith ice-cold ethyl ether and then discarded. The ether extracts weredried over K₂CO₃ and then filtered into a round-bottom flask and thesolvent removed on the rotavap at 0° C. After all of the solvent wasremoved, the residue was dissolved in 40 mL sieve dried CH₃CN, and tothis was added 870 mg NaI and 650 mg K₂CO₃. The flask was then attachedto a reflux condenser and a heating mantle and the system heated underreflux for 3 h. After this time, the flask was cooled to roomtemperature and filtered. The solvent was then removed on a rotavap andthe residue dissolved in 40 mL punctilious ethanol. To this mixture wasadded 750 mg NaBH₄ in one portion and the mixture allowed to stirovernight. On the following day, 1N HCl was added to this mixture untilno further evolution of hydrogen was observed. This was stirred for 10min, and then 50% NaOH and water were added until the mixture was clearand basic. The volatiles were then removed on a rotavap, and the residuewas extracted 3 times with 1:1 ethyl ether:ethyl acetate. This was driedover K₂CO₃ and Na₂SO₄. After filtration and solvent removal, a smallportion of the crude residue was dissolved in CHCl₃ and spotted on asilica gel plate. Elution with 50% CMA-80 (80 CHCl₃: 18 MeOH: 2 NH₄OH)in CHCl₃ revealed a compound in the mixture that gave a pale spot whendipped in 5% PMA in EtOH at about 0.75 Rf. This is the tertiary amineproduct. No other tertiary amines were observed in the mixture. ¹H NMRof the crude mixture revealed the desired product as well as startingmaterial (9) and other undesired products. Chromatography on silica gelusing 12.5% CMA-80 in CHCl₃ gave the desired product in the earlyfractions just behind the solvent front but not in the solvent front.This gave 115 mg of the desired product as a slightly yellow oil. Yield15.5%.

¹H NMR (CDC₃) δ 0.993 (s, 3H); 1.404 (ddd, 1H, J=13.7, 2.6, 2.6 Hz);2.149 (d, 1H, J=11.6 Hz); 2.229 (d, 1H, J=17.0 Hz); 2.240 (s, 3H); 2.310(dd, 1H, J=11.6, 1.5 Hz); 2.379 (ddd, 1H, J=12.1, 12.1, 3.2 Hz); 2.646(d, 1H, J=17.0 Hz); 2.862 (dd, 1H, J=13.7, 4.7 Hz); 2.885 (d, 1H, J=18.3Hz); 2.962 (m, 1H); 3.570 (d, 1H, J=18.3 Hz); 3.634 (s, 3H); 6.715 (ddd,1H, J=8.1, 2.5, 0.9 Hz); 6.839 (m, 2H); 7.048 (d, 1H, J=7.6 Hz);7.197-7.080 (m, 4H). ¹³C NMR (CDCl₃) δ 158.9, 148.9, 135.9, 135.6,128.6, 128.36, 128.0, 125.9, 125.5, 120.0, 113.9, 110.8, 64.04, 54.9,52.2, 46.6, 40.6, 40.11, 35.98, 31.5, 24.4.

(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-2,10a-dimethylbenzo-[g]isoquinoline(7): To a 10 mL single-necked flask was added 100 mg (0.31 mmol) of(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-methoxyphenyl)-2,10a-dimethylbenzo[g]isoquinoline(10) and 0.8 mL of glacial acetic acid and 0.8 mL of 48% HBr. Thismixture was heated under reflux for 18 h and then cooled to roomtemperature. The pH was then adjusted to 10 with cooling starting with50% NaOH and finishing with saturated NaHCO₃. This was extracted 2 timeswith CHCl₃ and 2 times with 3:1 n-butanol:toluene. Both extracts weredried over K₂CO₃, and then the solvent was removed. The material fromboth extracts was examined by ¹H NMR and was shown to contain thedesired product. The material from the CHCl₃ layer was chromatographedon silica gel eluting with 25d% CMA-80 in CHCl₃. This gave 27 mg of thedesired pro duct (7) (28% yield). The residue was dissolved in MeOH, andto this was added 3 equivalents of 1N HCl in dry ethyl ether. Thesolvents were removed, and the residue crystallized from ether/MeOH. Thebutanol extracts contained 45 mg of the desired material giving anoverall yield of 74.6%. MP ° C. 270-275 (dec). Anal. Calcd forC₂₁H₂₆NOCl.0.25H₂O: C, 65.54; H, 7.20; N, 3.64. Found: C, 65.86; H,7.15; N, 3.42. ¹H NMR (DMSO) δ 1.014 (s, 3H); 1.587 (d, 1H, J=14.3 Hz);2.072 (s, 3H); 2.358 (d, 1H, J17.4 Hz); 2.498 (d, 1H, J=17.4 Hz); 2.734(s, 3H); 2.924-2.792 (m, 3H); 3.113 (d, 1H, J=13.1 Hz); 3.602 (d, 1H,J=18.78 Hz); 6.562 (d, 1H, J=8.0 Hz); 6.611 (m, 2H); 6.993 (t, 1H, J=7.5Hz); 7.081 (d, 1H, J=7.5 Hz); 7.148 (t, 1H, J=7.8 Hz); 7.269-7.193 (m,2H); 9.30 (s, 1H); 9.898 (bs, 1H). ¹³C NMR (DMSO) δ 156.7, 146.4, 135.5,133.3, 128.5, 128.4, 128.2, 126.2, 125.7, 117.6, 114.3, 113.5, 59.2,49.4, 38.6, 35.4, 35.2, 31.0, 28.7, 22.8.

(±)-1,2,3,4,4a,5,10,10a-octahydro-4a-(3-hydroxyphenyl)-2-phenethyl-10a-methylbenzo[g]isoquinoline(8): To 300 mg (0.93 mmol) intermediate (10) was added 5 mL dry toluenefollowed by heating to 80° C. To this was added 0.23 mL (1.86 mmol)distilled phenylchloroformate dropwise via syringe. A precipitateformed, and the mixture was heated at reflux for 5 h. The mixture wascooled to room temperature and washed 3 times with 1N NaOH and driedover sodium sulfate. ¹H NMR of the crude mixture indicated that nostarting material was present (no N-methyl signal at 2.25 ppm). Thecrude mixture was then dissolved in 4 mL glacial acetic acid and 4 mL48% HBr. This was heated at reflux for 18 h followed by addition ofwater and methyl t-butyl ether (MTBE). The aqueous layer was removed andextracted two more times with MTBE to remove phenol. The aqueous layerwas then pH adjusted to 10 using 50% NaOH and saturated sodiumbicarbonate and extracted 3 times with 3:1 methylenechloride:tetrahydrofuran (THF) and the organic layer dried over sodiumsulfate. Following removal of solvent, this highly polar material wasdissolved in 15 mL THF, and to this was added 442 mg (1 mmol) BOPreagent, 0.4 mL triethylamine (2.2 mmol), and 136 mg (1 mmol) phenylacetic acid. This was stirred for 3 h and then diluted with ethyl ether,40 mL, and washed sequentially with 15 mL water, 1N HCl, saturatedsodium bicarbonate, and brine. The solution was dried over sodiumsulfate and the solvent removed on a rotary evaporator. The material wasthen dissolved in chloroform and filtered through silica gel to removehighly colored polar impurities to give 142 mg relatively cleanmaterial. ¹H NMR of this crude material indicated the presence ofrotamers typical of piperidine amides and urethanes. Reduction of thiscompound was accomplished by dissolving in dry THF followed by additionof 1.16 mL of 2M borane dimethylsulfide in THF. After heating for 3 h,the mixture was cooled to room temperature, and 2 mL methanol was addedand stirred for 1 h. After this time, 1.16 mL 1N HCl in ether was addedand stirred for 1 h. The solvent was then removed on a rotary evaporatorand the crude mixture dissolved in chloroform, saturated sodiumbicarbonate, and water. The pH was adjusted to 10 and the organic layerwashed 3 times with water and then dried over sodium sulfate. The cruderesidue was chromatographed on silica gel using 0-10% MeOH in chloroformas eluent, and this material was crystallized from MeOH/ether as its HClsalt to give 55.8 mg of the desired material (0.137 mmol) or 2.2%overall yield. MP ° C. 255-265 (dec). Anal. Calcd for C₂₈H₃₂NOCl.0.5H₂O:C, 75.91; H, 7.51; N, 3.16. Found: C, 75.93; H, 7.53; N, 3.17. ¹H NMR(DMSO) δ 10.06 (br s, 1H); 9.34 (s, 1H); 7.30 (dd, 2H, J=8.1 Hz, 8.1Hz); 7.22 (m, 5H); 7.15 (dd, 1H, J=7.7 Hz, 7.7 Hz); 7.08 (d, 1H, J=7.7Hz); 6.63 (s, 1H); 6.62 (d, 1H, J=8.1 Hz); 6.55 (d, 1H, J=8.1 Hz); 3.59(d, 1H, J=18.9 Hz); 3.50 (d, 1H, J=12.1 Hz); 3.32 (m, 4H); 3.11 (ddd,1H, J=5.1 Hz, 12.1 Hz, 12.1 Hz); 3.02 (ddd, 1H, J=5.1 Hz, 12.1 Hz, 12.1Hz); 2.87 (m, 3H); 2.50 (d, 1H, J=17.4); 2.42 (d, 1H, J=17.4); 1.62 (d,1H, J=14.3); 1.08 (s, 3H). ¹³C NMR (DMSO) δ 156.72, 146.44, 137.23,135.45, 133.38, 128.63, 128.59, 128.56, 128.52, 128.19, 126.71, 126.39,125.72, 117.55, 114.33, 113.51, 57.27, 57.18, 48.22, 39.46, 38.66,35.40, 35.21, 29.45, 28.59, 23.06.

References

(1) Evans, D. A.; Mitch, C. H.; Thomas, R. C.; Zimmerman, D. M.; Robey,R. L. Application of metalated enamines to alkaloid synthesis. Anexpedient approach to the synthesis of morphine-based analgesics. J. Am.Chem. Soc. 1980, 102, 5955-5956. WARNING: Read the backgroundinformation relating to analogs of MPTP (i.e., 9) including Zimmerman etal., J. Med. Chem., 1986, 29, 1517-1520, and references cited therein.

(2) Zimmerman, D. M.; Smits, S.; Nickander, R. Further investigation ofnovel 3-methyl-4-phenylpiperidine narcotic antagonists. In Proceedingsof the 40th Annual Scientific Meeting of the Committee on Problems ofDrug Dependence, 1978, pp. 237-247.

(3) Mitch, C. H.; Leander, J. D.; Mendelsohn, L. G.; Shaw, W. N.; Wong,D. T.; Zimmerman, D. M.; Gidda, S. J.; Cantrell, B. E.; Scoepp, D. D.;Johnson, B. G.; Leander, J. D. J. Med. Chem. 1994, 37, 2262-2265.

(4) Xu, H.; Lu, Y.-F.; Partilla, J. S.; Brine, G. A.; Carroll, F. I.;Rice, K. C.; Lai, J.; Porreca, F.; Rothman, R. B. Opioid peptidereceptor studies. 6. The 3-methylfentanyl congeners RTI4614-4 and itsenantiomers differ in efficacy, potency, and intrinsic efficacy asmeasured by stimulation of [³⁵S]GTP-γ-S binding using cloned μ-opioidreceptors. Analgesia 1997, 3, 3542.

TABLE 4 Radioligand Binding Results in Mu, Delta, and Kappa OpioidReceptor Assays K_(i) (nM ± SD) Compound [³H]DAMGO^(a) [³H]DADLE^(b)[³H]U69,593^(c) 7 297 ± 23  >5710 166 ± 15  (1.02 ± 0.07) (0.87 ± 0.06)8 11.2 ± 2.7  1270 ± 106 9.8 ± 1.7 (0.56 ± 0.07)  (1.14 ± 0.099) (0.69 ±0.07) 3, naltrexone 1.39 ± 0.40 94.9 ± 6.6 4.71 ± 0.12 (0.94) (1.01)(1.05) ^(a)[³H]DAMGO [(D-Ala²,MePhe⁴,Gly-ol⁵)enkephalin]. Tritiatedligand selective for mu opioid receptor. ^(b)[³H]DADLE[(D-Ala²,D-Leu⁵)enkephalin]. Tritiated ligand selective for delta opioidreceptor. ^(c)[³H]U69,593(trans-3,4-dichloro-N-methyl[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide).Tritiated ligand selective for kappa opioid receptor.

I? !

TABLE 5 Affinities of the 4-Phenylpiperidine Antagonists for the μ and κOpioid Receptors^(a) K_(i) (nM) Compd [³H]Nal^(b) [³H]EKC^(c) 5 80 833 61.5 52 3, naltrexone 0.56 3.9 ^(a)Data taken from reference 3.^(b)Naloxone (μ receptor assay). ^(c)Ethylketocyclazocine (κ receptorassay).

TABLE 6 Inhibition by Antagonists of [³⁵S]GTPγS Binding in Guinea PigCaudate Stimulated by the Opioid Receptor Subtype-Selective Agonists,DAMGO (μ), SNC80 (δ), and U69,593 (κ). K_(i) (nM ± SD) (N) CompoundDAMGO SNC80^(a) U69,593 7  119 ± 7.93  222 ± 30.7 52.60 ± 6.38  (0.94 ±0.06) (0.78 ± 0.09) (1.10 ± 0.14) 8   10 ± 0.91  184 ± 24.3 6.61 ± 0.57(0.89 ± 0.06) (0.78 ± 0.09) (1.01 ± 0.08) 1, naltrexone 0.930 ± 0.21 19.3 ± 2.25 2.05 ± 0.21 (1.00 ± 0.22) (1.13 ± 0.14) (0.76 ± 0.05)^(a)SNC80([(+)-4-[(αR)-α-(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide]).Agonist selective for delta opioid receptor.

a SNC80([(+)-4-[(αR)-α-(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide]).Agonist selective for delta opioid receptor.

This Example is described in Thomas et al, Bioorganic and MedicinalChemistry Letters 8 (1998) 3149-3152, incorporated herein by reference.

Example 3 Opioid Receptor Antagonists

Summary

Two sets of novel opioid receptor antagonist pharmacophores have beenprepared and demonstrated from a model of opioid antagonist binding. Oneis based on a rigid 5-phenylmorphan nucleus and the other on a moreflexible benzoisoquinoline nucleus. Using modifications of these systemsand by comparisons with the relatedtrans-3,4-dimethyl-4-(3-hydoxyphenyl)piperidines, provides strongevidence supporting the hypothesis that this class of antagonist bindsthe opioid receptors in a phenyl equatorial mode and that thetrans-3-methyl substituent (phenyl piperidine numbering) is an importantelement for conversion of agonists into antagonists.

Chemistry

The β-3-5-(3-hydroxyphenyl) morphans were prepared by the method shownin FIG. 11. Deprotonation of the known compound 10 with sec-butyllithium followed by alkylation with allyl bromide cleanly providedintermediate 11 in quantitative yield. This compound was then cyclizedprovide 12 in 90% yield as a 2.5:1 mixture of diastereomers. Furtherexperimentation established conditions which changed the ratio of12a:12b to 10:1. Compounds 13a,b were then readily available via enaminereduction followed by separation using radial chromatography. The majorisomer 13 was then O-demethylated to give 14. Since elucidation of thestereochemistry was not straightforward using NMR techniques, crystalsof the HCl salt of 14 are shown by X-ray analysis to possess the desired9β-methyl stereochemistry.

Compound 13 was also converted to the N-phenylethyl compound 18.N-Demethylation of 13 gave 15 which on O-demethylation yielded 16.Compound 16 was then converted to the N-phenethyl derivative (18) by thetwo step procedure involving coupling of 16 with phenylacetic acidfollowed by borane-dimethylsulfide reduction of the intermediate amide17.

The benzoisoquinoline compound (20) was also prepared starting fromcompound 10 according to the method illustrated in FIG. 12. Accordingly,10 was deprotonated with sec-butyl lithium followed by alkylation withα,α′-dichloro-xylene to give intermediate 19 which was not isolated butwas immediately cyclized with NaI and reduced to provide compound 20 in13% yield. O-Demethylation of 20 using hydrogen bromide in acetic acidyielded 21. The structure was established using a combination of NMRtechniques.

Biological Assay Results

The new compounds 14, 18, and 21 were shown to bind the opioid receptorsand also were shown to be pure antagonists. The data supporting theseconclusions is presented in Tables 7 and 8.

Discussion

The radioligand binding data in Table 7 show that compounds 14, 18, and21 have affinity for the opioid receptors 18 is more potent than 14. Thedata in Table 8 shows that all three compounds are pure antagonists.

Experimental

All of the solvents used were reagent grade with the exception ofdiethyl ether and THF in reactions and these were distilled fromsodium/benzophenone ketyl. NMR spectra were collected on both a 250 MHzand a 500 MHz Bruker spectrometer. The melting points reported below areuncorrected.

1,2,3,4-Tetrahydro-4-allyl-1,5-dimethyl-4-(m-methoxyphenyl)pyridine (5):To a solution of 500 mg (2.3 mmol) of tetrahydropyridine 10 in 15 mL ofTHF at 42° C. was added s-BuLi in cyclohexane (1.3M, 2.9 mmol). After 1h, allyl bromide (2.3 mmol) was added, and the color of the solutionchanged from dark red to yellow. After been stirred for 1 hour at −42°C., the mixture was allowed to warmed to 0° C. and then quenched withwater (10 mL). Diethyl ether (10 mL) was added and the aqueous layer wasextracted with ether (2×). The combined ether layers were washed withwater (10 mL), saturated NaHCO₃, brine and dried over Na₂SO₄.Evaporation of solvent afforded 590 mg (˜100%) of crude 11. The crudeproduct was used directly in the next step without further purification.¹H NMR (CDCl₃) δ 7.26 (m, 1H), 7.01 (m, 2H), 6.74 (m, 1H), 5.89 (s, 1H),5.82 (m, 1H), 5.13 (m, 2H), 3.80 (s, 3H), 2.68-2.40 (m, 3H), 2.55 (s,3H), 2.22 (m, 1H), 1.66 (m, 2H), 1.52 (s, 3H). ¹³C NMR (CDCl₃) δ 159.2,151.1, 136.7, 135.8, 128.7, 119.8, 117.4, 114.3, 110.1, 107.7, 55.1,46.1, 43.1, 43.0, 41.7, 36.4, 17.3.

(1S*,5R*,9R*/S*)-2,9-Dimethyl-5-(m-methoxyphenyl)-2-azabicyclo[3,3,1]non-3-ene(12a/b): A solution of 300 mg (1.17 mmol) of 11 in 6 mL of 85%H₃PO₄/HCO₂H (1:1) was stirred at room temperature for 72 h. Theresulting dark brown mixture was diluted with water (6 mL) and cooled inice bath while NaOH (25% w/w) was added until pH-8. The aqueous solutionwas extracted with CHCl₃ (3×). The combined organic layers was washedwith aqueous NaHCO₃ and brine and dried over Na₂SO₄. Evaporation of thesolvent gave 270 mg (90%) of crude products 12a and 12b in a ratio of2.5:1. The crude products were used directly in the next step withoutfurther purification. ¹H NMR (CDCl₃) of the mixture: δ 7.24-6.70 (m,4H), 6.16 (d, 1H, J=9.2 Hz), 4.34 (d, 1H, J=7.0 Hz), 4.13 (d, 1H, J=9.1Hz), 3.80 (s, 3H), 2.80 (s, 3H), 3.10-1.40 (m, 8H), 0.74(d, 3H, J=8.6Hz), 0.57 (d, 3H, J=8.1 Hz).

(1S*,5R*,9R*/S*)-2,9-Dimethyl-5-(m-methoxyphenyl)-2-azabicyclo[3,3,1]nonane(13a/b): A solution of 270 mg (1.05 mmol) of 12a and 12b mixture andacetic acid (1.05 mmol, 0.061 mL) in 5 mL of dichloroethane was treatedwith NaBH(OAc)₃ under N2 atmosphere. The reaction was stirred at roomtemperature for 2 h. The reaction was quenched by adding 10% NaOH topH˜10. The mixture was extracted with ether (3×), washed with water andbrine. The organic phase was dried over Na₂SO₄ and concentrated underreduced pressure. Separation by chromatography (1% Et3N/EtOAc) gave 135mg (50%) of 13a and 60 mg (22%) of 13b as colorless oils. ¹H NMR (CDCl₃)of 8: δ 7.26 (m, 1H,), 6.94 (m, 2H), 6.70 (m, 1H), 3.80 (s, 3H),3.05-2.90 (m, 2H), 2.71 (m, 1H), 2.43 (s, 3H), 2.42-2.30 (m, 2H),2.28-2.15 (m, 1H), 2.00-1.35 (m, 6H), 0.86 (d, 3H, J=8.25 Hz). ¹H NMR(CDCl₃) of 9: δ 7.23 (m, 1H,), 6.96 (m, 2H), 6.72 (m, 1H), 3.81 (s, 3H),3.10-2.98 (m, 2H), 2.90 (m, 1H), 2.75 (m, 1H), 2.50 (s, 3H), 2.47 (m,1H), 2.30-2.06 (m, 2H), 2.05-1.95 (m, 2H), 190-1.50 (m, 4H), 0.75 (d,3H, J=8.56 Hz). ¹³C NMR (CDCl₃) of 8: 159.2, 152.0, 128.9, 118.0, 112.3,109.6, 59.7, 55.1, 51.1, 43.1, 42.5, 40.0, 38.3, 29.1, 25.6, 23.4, 14.8.Anal. Calcd for Cl₇H₂₅NO: C, 78.72; H, 9.71; N, 5.40. Found: C, 78.79;H, 9.75; N, 5.34.

(1S*,5R*,9R*)-2,9-Dimethyl-5-(m-hydroxyphenyl)-2-azabicyclo[3,3,1]nonane(14): Compound 13a was treated with 4 mL of glacial acetic acid and 4 mLof 48% aqueous hydrobromic acid at reflux temperature for 20 h. Thereaction was cooled to room temperature and diluted with 10 mL of water.The pH was adjusted to 10 by using 50% NaOH with ice cooling. Theproduct was extracted into a mixture of 3:1 1-butanol/toluene, driedover Na₂SO₄, and concentrated under reduced pressure. Separation bychromatography (½CMA 80) provided 199 mg (84%) of 10 as a white solid.¹H NMR (CDCl₃) δ 7.15 (m, 1H,), 6.87-6.75 (m, 2H), 6.61 (m, 1H),3.10-2.90 (m, 2H), 2.77 (m, 1H), 2.44 (s, 3H); 2.50-2.30 (m, 2H),2.25-2.10 (m, 1H), 2.00-1.60 (m, 5H), 1.60-1.40 (m, 1H), 0.80 (d, 3H,J=8.3 Hz). ¹³C NMR (CDCl3) δ 155.9, 152.0, 129.1, 117.5, 113.0, 112.4,59.7, 51.0, 43.0, 42.0, 40.2, 38.0, 29.0, 25.6, 23.2, 14.6. Anal. Calcdfor C₁₆H₂₃NO.HCl: C, 68.19; H, 8.53; N, 4.97. Found: C, 68.25; H, 8.53;N, 5.03. The structure of this compound was determined by single crystalX-ray analysis.

(1S*,5R*,9R*)-5-(m-Hydroxyphenyl)-9-methyl-2-azabicyclo[3,3,1]nonane(15): A solution of 200 mg (1.28 mmol) of phenyl chloroformate was addeddropwise to 300 mg (1.16 mmol) of 13a in 10 mL of dichloromethane atroom temperature under a nitrogen atmosphere. The reaction was refluxedfor 6 h. Since the reaction was not complete by TLC, the solvent wasthen changed to dichloroethane and the reflux was continued for another12 h. The mixture was cooled to room temperature and concentrated underreduced pressure. The resulting oil was treated with 10 mL of 1N NaOHand stirred with slight warming for 15 min. The product carbamate wasthen extracted with ether, and the ether layer was washed with 1N HCland water. The organic phase was dried over Na₂SO₄ and concentratedunder reduced pressure. The residue was then treated with 5 mL ofethanol and 1.5 mL of 50% aqueous KOH at reflux for 70 h. The mixturewas cooled and concentrated under reduced pressure. The resultingconcentrate was extracted with ether (2×), and the ether layers wereconcentrated in vaccuo. The resulting oil was dissolved into 10 mL of 1N HCl and washed with ether. The aqueous layer was then made stronglybasic (pH>12) with 50% NaOH with ice cooling. The desired amine 15 wasextracted into ether (2×), and the ether extracts were washed , driedover Na₂SO₄, and concentrated under reduced pressure to give 207 mg(70%) of crude 11 as light yellow oil. The crude compound 15 was treatedwith 4 mL of glacial acetic acid and 4 mL of 48% aqueous hydrobromicacid at reflux temperature for 20 h. The reaction was cooled to roomtemperature and diluted with 10 mL of water. The pH was adjusted to 10by using 50% NaOH with ice cooling. The product was extracted into amixture of 3:1 1-butanol/toluene, dried over Na₂SO₄, and concentratedunder reduced pressure to yield 100 mg (51%) of 16 as a semi solid. Thecrude product 16 was used directly in the next step without furtherpurification. ¹H NMR (CD₃OD) δ 7.15 (m, 1H,), 6.79-6.75 (m, 2H), 6.65(m, 1H), 3.70-3.30 (m, 3H), 2.70 (m, 1H), 2.45-1.70 (m, 8H), 0.87 (d,3H, J=8.3 Hz).

(1S*,5R*,9R*)-5-(m-Hydroxyphenyl)-9-methyl-2-[(phenylmethyl)carbonyl]-2-azabicyclo[3,3,1]nonane(17): To a solution of 100 mg (0.43 mmol) of 16 and 190 mg (0.43 mmol)of BOP reagent and 0.19 mL (1.3 8 mmol) of triethylamine in 15 mL of THFwas added phenylacetic acid (70.25 mg, 0.52 mmol). The mixture wasstirred at room temperature for 1 h. The reaction was diluted with 10 mLof water and ether (10 mL). The aqueous layer was extracted with ether(2×). The combined ether layers were washed with NaHCO₃ and brine, anddried over Na₂SO₄. Evaporation of solvent provided the crude product 17as a colorless oil. (A spectrum of ¹H NMR was attached but the NMR datawas not interpreted here due to the rotamers).

(1S*,5R*,9R*)-5-(m-Hydroxyphenyl)-9-methyl-2-(2′-phenylethyl)-2-azabicyclo-[3,3,1]nonane(18): The crude amide 17 was dissolved in THF (8 mL). The solution wascooled to 0° C., and Borane:methyl sulfide complex (0.4 mL, 0.8 mmol)was added dropwise. After vigorous reaction ceased, the resultingmixture was slowly heated to reflux and maintained at that temperaturefor 4 h. The reaction mixture was cooled to 0° C., 6 mL of methanol wasadded , and the mixture was stirred for r 1 h. Anhydrous hydrogenchloride in ether (1 mL) was added to attain a pH<2, and the resultingmixture was gently refluxed for 1 h. After the mixture was cooled toroom temperature, methanol was added and the solvents were removed on arotovapor. The residue obtained was made basic (pH>12) by adding 25%NaOH and extracted with ether (3×). The combined ether layers were driedover Na₂SO₄ and concentrated under reduced pressure. Separation bychromatography (1% Et₃N/50% EtOAc/hexanes) gave 38 mg (71%) of amine 18as a colorless oil. ¹H NMR (CDCl₃) δ 7.30-7.14 (m, 6H), 6.85 (m, 2H),6.63 (m, 1H), 4.71 (br s, 1H), 3.05 (m, 2H), 2.88 (m, 1H), 2.79 (s, 4H),2.43-2.15 (m, 3H), 1.94-1.65 (m, 5H), 1.65-1.45 (m, 1H), 0.83 (d, 3H,J=8.2 Hz). ¹³C NMR (CDCl3) δ 155.7, 152.5, 140.9, 129.1, 128.8, 128.3,125.9, 117.7, 113.0, 112.4, 57.4, 57.2, 49.5, 42.4, 40.0, 38.7, 34.1,29.1, 26.2, 23.4, 14.7. Anal. Calcd for C₂₃H₂₉NO.HCl: Calcd: C, 74.27;H, 8.13; N, 3.77. Found: C, 74.16; H, 8.12; N, 3.71.

(±)-(2,8a)-Dimethyl-4a-(3-Methoxyphenyl)-Octahydrobenzo[e]Isoquinoline(19): To a dry three neck round bottomed flask was charged 500 mg (2.3mmol) of 10 and 20 mL dry THF. This was cooled to −78° C. and to thiswas added 2.4 mL (3.12 mmol) s-BuLi (1.3M in cyclohexane) via a syringeover 5 minutes. The flask was then warmed to −20° C. and aged for 30min. The flask was then cooled to −78° C. and cannulated into a mixtureof 40 mL dry ethyl ether and 1.3 g (7.59 mmol) α,α′-dichloro xylene at−50° C. over 20 min. This was aged for 20 min. and then quench withice-cold 1N HCl. The contents of the flask were then transfered to aseparatory funnel with ice-cold ether and ice-cold 1N HCl. The aqueouslayer was removed and stored in an ice bath while the organic layer wastwice extracted with ice-cold 1N HCl. The combined aqueous layers wereplaced into a new separatory funnel and extracted twice with ice-coldethyl ether. The aqueous layer was then made basic with 50% NaOH atfirst and finally sat'd NaHCO₃ to pH 10. The aqueous layer was thenextracted 3 times with ice-cold ethyl ether and then discarded. Theether extracts were dried over K₂CO₃ and then filtered into a roundbottom flask and the solvent removed on the rotavap at 0° C. After allof the solvent was removed, the residue was dissolved in 40 mL seivedried CH₃CN and to this was added 870 mg NaI and 650 mg K₂CO₃. The flaskwas then attached to a reflux condenser and a heating mantle and thesystem heated under reflux for 3 hours. After this time, the flask wascooled to room temperature and filtered. The solvent was then removed ona rotavap and the residue dissolved in 40 mL punctillious ethanol. Tothis mixture was added 750 mg NaBH₄ in one portion and the mixtureallowed to stir overnight. On the following day, 1N HCl was added tothis mixture until no further evolution of hydrogen was observed. Thiswas stirred for 10 min and then 50% NaOH and water were added until themixure was clear and basic. The volatiles were then removed on a rotavapand the residue was extracted 3 times with 1:1 ethyl ether: ethylacetate. This was dried over K₂CO₃ and Na₂SO₄. After filtration andsolvent removal, a small portion of the crude residue was dissolved inCHCL₃ and spotted on a silica gel plate. Elution with 50% CMA-80 inCHCL₃ revealed a compound in the mixture that gave a pale spot whendipped in 5% PMA in EtOH at about 0.75 Rf. This is the 3° amine product.No other 3° amines were observed in the mixure. ¹H NMR of the crudemixture revealed the desired product as well as starting material 10 andother undesired products. Chromatography on silica gel using 12.5%CMA-80 in CHCL₃ gave the desired product in the early fractions justbehind the solvent front but not in. the solvent front. This gave 115 mgof the desired product as a slightly yellow oil. Yield 15.5%.

¹H NMR (CDCl₃): δ 0.993 (s, 3H); 1.404 (ddd, 1H, J=13.7, 2.6, 2.6 Hz);2.149 (d, 1H, J=11.6 Hz); 2.229 (d, 1H, J=17.0 Hz); 2.240 (s, 3H); 2.310(dd, 1H, J=11.6, 1.5 Hz); 2.379 (ddd, 1H, J=12.1, 12.1, 3.2 Hz); 2.646(d, 1H, J=17.0 Hz); 2.862 (dd, 1H, J=13.7, 4.7 Hz); 2.885 (d, 1H, J=18.3Hz); 2.962 (m, 1H); 3.570 (d, 1H, J=18.3 Hz); 3.634 (s, 3H); 6.715 (ddd,1H, J=8.1, 2.5, 0.9 Hz); 6.839 (m, 2H); 7.048 (d, 1H, J=7.6 Hz);7.197-7.080 (m, 4H).

¹³C NMR (CDCl₃): d 158.9, 148.9, 135.9, 135.6, 128.6, 128.36, 128.0,125.9, 125.5, 120.0, 113.9, 110.8, 64.04, 54.9, 52.2, 46.6, 40.6, 40.11,35.98, 31.5, 24.4.

(±)-(2,8a)-Dimethyl-4a-(3-Hydroxyphenyl)-Octahydrobenzo[e]Isoquinoline(20): To a 10 mL single necked flask was added 100 mg (0.31 mmol) of(±)-(2,8a)-dimethyl-4a-(3-methoxyphenyl)-octahydrobenzo[e]isoquinolineand 0.8 mL of glacial acetic acid and 0.8 mL of 48% HBr. This mixturewas heated under reflux for 18 hours and then cooled to roomtemperature. The pH was then adjusted to 10 with cooling starting with50% NaOH and finishing with sat'd NaHCO₃. This was extracted 2 timeswith CHCl₃ and 2 times with 3:1 n-butanol:toluene. Both extracts weredried over K₂CO₃ and then the solvent was removed. The material fromboth extracts was examined by ¹H NMR and was shown to contain thedesired product. The material from the CHCl₃ layer was chromatographedon silica gel eluting with 25% CMA-80 in CHCl₃. This gave 27 mg of thedesired product 20 (28% yield). The residue was dissolved in MeOH and tothis was added 3 equivalents of 1N HCl in dry ethyl ether. The solventswere removed and several attempts were made to crystallize form ethylacetate/MeOH. This only provided an oil. The same result was obtainedwith ethyl ether/MeOH. Finally, ethyl acetate was added to the residueand warmed and the solvent removed on a rotavap. This process wasrepeated 5 times and the solid thus formed was placed on a high vacuumpump overnight. MP ° C. 270-275 (dec). C, H, N.

¹H NMR (DMSO): δ 1.014 (s, 3H); 1.587 (d, 1H, J=14.3 Hz); 2.072 (s, 3H);2.358 (d, 1H, J=17.4 Hz); 2.498 (d, 1H, J=17.4 Hz); 2.734 (s, 3H);2.924-2.792 (m, 3H); 3.113 (d, 1H, J=13.1 Hz); 3.602 (d, 1H, J=18.78Hz); 6.562 (d, 1H, J=8.0 Hz); 6.611 (m, 2H); 6.993 (t, 1H, J=7.5 Hz);7.081 (d, 1H, J=7.5 Hz); 7.148 (t, 1H, J=7.8 Hz); 7.269-7.193 (m, 2H);9.30 (s, 1H); 9.898 (bs, 1H).

¹³C NMR (DMSO): δ 156.7, 146.4, 135.5, 133.3, 128.5. 128.4, 128.2,126.2, 125.7, 117.6, 114.3, 113.5, 59.2, 49.4, 38.6, 35.4, 35.2, 31.0,28.7, 22.8.

The butanol extracts contained 45 mg of the desired material giving anoverall yield of 74.6%.

TABLE 7 Radioligand Binding Results at all Three Opioid Receptors forNew Antagonist Pharmacaphores IC₅₀ (nM ± SD) Compound # RTI # [³H]DAMGO^(a) [³H] DADLE^(b) [³H] U69,593^(c) (14) 5989-30 243.7 ±21.9  >10,000  1470 ± 28.4  (1.00 ± 0.08) (0.89 ± 0.06) (18) 5989-314.54 ± 0.21 457.4 ± 50.5  27.2 ± 1.89 (1.08 ± 0.05) (0.88 ± 0.08) (1.25± 0.11) (21) 5989-28  406 ± 31.9 >10,000 306.4 ± 28.4  (1.02 ± 0.07)(0.81 ± 0.06) ^(a)Tritiated ligand selective for mu opioid receptor.^(b)Tritiated ligand selective for delta opioid receptor. ^(c)Tritiatedligand selective for kappa opioid receptor.

TABLE 8 IC₅₀ Data for New Antagonists Toward Reversal of AgonistStimulated GTP Binding IC₅₀ (nM ± SD) Compound # RTI # DAMGO^(a) SNC80^(b) U69,593^(c) (14) 5989-30 288 ± 78  >1000 >1000 (18) 5989-31 5.96± 0.72 >1000 26.3 ± 8.3 (21) 5989-28 NA NA 1552 ± 164 ^(a)Agonistselective for mu opioid receptor. ^(b)Agonist selective for delta opioidreceptor. ^(c)Agonist selective for kappa opioid receptor.

Example 4 κ-Selective N-Substituted Piperidines

Summary

The inhibition of radioligand binding and [³⁵S]GTPγS functional assaydata for N-methyl- and N-phenethyl-9β-methyl-5-(3-hydroxyphenyl)morphans(5b and 5c) (FIG. 13) show that these compounds are pure antagonists atthe μ, δ, and κ opioid receptors. Since 5b and 5c have the5-(3-hydroxyphenyl) group locked in a conformation comparable to anequatorial group of a piperidine chair conformation, this informationprovides very strong evidence that opioid antagonists can interact withopioid receptors in this conformation. In addition, it suggests that thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine class of antagonistoperates via a phenyl equatorial piperidine chair conformation.

Chemistry

The synthesis of the N-methyl- andN-phenethyl-9β-methyl-5-(3-hydroxyphenyl)-morphans (5b and 5c,respectively) was achieved as illustrated in FIG. 13. Treatment of1,2,6-trihydro-1,3-dimethyl-4-(3-methoxy)pyridine (6) with sec-butyllithium followed by quenching with allyl bromide provided the enamineadduct (7) which was cyclized without isolation to give2,9-dimethyl-5-(3-methoxyphenyl)-2-azabicyclo[3.3.1]non-3-ene (8a,b) ina 3:1 9β- to 9α-methyl ratio, using hydrochloric acid intetrahydrofuran. Reduction of unpurified 8a,b using sodium borohydridetriacetate followed by separation of the major isomer gave 9. Subjectionof 9 to O-demethylation using hydrobromic acid in acetic acid providedthe desired phenylmorphan (5b). Single crystal X-ray analysis showedthat 5b had the desired 9β-methyl relative configuration (FIG. 14). TheN-phenethyl derivative (5c) was prepared from intermediate 9. Treatmentof 9 with phenylchloroformate followed by hydrolysis of the resultingurethane with potassium hydroxide followed by O-demethylation withhydrobromic acid in acetic acid gave 10. Compound 10 was converted to 5cby coupling with phenyl acetic acid in the presence ofbenzotriazol-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphatefollowed by borane reduction of the resulting amide intermediate.

Biological Results

Table 9 lists the radioligand binding data for compounds 5b and 5c alongwith data for naltrexone. While the binding of 5b to all three opioidreceptors was weak, it is particularly interesting to note that changingthe N-substituent from methyl to phenethyl (5c) provided a dramaticincrease in binding affinity, a feature shared by the corresponding4-(3-hydroxyphenyl)piperidine analogs (4a and 4b, Table 10).²Furthermore, the relative binding affinities displayed by 5b and 5c formu and kappa opioid receptors are quite similar to that observed for 4aand 4b. These results show that the binding affinities of 5b and 5c arenot adversely affected by the 1,5-carbon bridge present in thesestructures. In addition, it suggests a common binding mode for the twotypes of structures.

The increase in binding of [³⁵S]GTPγS stimulated by opioid agonists isan assay able to distinguish compounds of differing efficacy andintrinsic activity.³ The antagonist properties of test compounds can bedetermined by measuring the inhibition of this stimulation. To assesstheir potency as antagonists and to verify that 5b and 5c retain pureantagonist activity, the compounds were analyzed for either stimulationor inhibition of agonist stimulated GTP binding in comparison withnaltrexone (Table 11). In this functional assay, neither 5b nor 5cstimulated GTP binding as measured up to concentrations of 10 μM,showing that both compounds were devoid of agonist activity.⁴ Asmentioned previously, retention of pure antagonist activity regardlessof the N-substituent structure is a key feature that separates the3,4-dimethyl-4-(3-hydroxyphenyl)-piperidine class of antagonist fromoxymorphone-based antagonists which display pure antagonism only forcertain N-substituents such as the N-allyl or N-cyclopropylmethylderivatives. In their ability to reverse agonist-stimulated GTP binding,compound 5c displayed a higher potency than naltrexone. These resultsare striking since agonist activity in several opioid ligands isenhanced by N-substituents with two methylene groups terminated by aphenyl group (N-phenethyl). It is evident that the antagonist activityof 5c is due to factors different from those of the oxymorphone-typepure antagonists.

The data in Table 11 also demonstrates that the N-methyl to N-phenethylchange, 5b to 5c, results in a concomitant increase in antagonistpotency. Thus, as is the case for the3,4-dimethyl-4-(3-hydroxyphenyl)piperidines, the antagonist potency andnot the agonist/antagonist behavior of the9β-methyl-5-(3-hydroxyphenyl)morphans (5b and 5c) is mediated by theN-substituent.

Discussion

These experiments demonstrated that N-methyl9β-methyl-5-(3-hydroxyphenyl)morphan (5b) is an opioid receptor pureantagonist. In addition, replacing the N-methyl with an N-phenethylgroup to give 5c resulted in a 63-, 60-, and 70-fold increase inantagonist potency at the mu, delta, and kappa opioid systems. Theseresults are particularly important since changing an N-methyl to anN-phenethyl substituent in all opioid systems which have the3-hydroxyphenyl group in an axial relationship relative to thepiperidine ring results in an increase in opioid agonist activity.⁵ Thisinformation strongly suggests that 5b and 5c are acting asconformationally rigid analogs of thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine class of opioidantagonists where the 3-hydroxyphenyl group is in an equatorial positionrelative to the piperidine ring.

In opioid alkaloids like naloxone (1a) and naltrexone (1b), the3-hydroxyphenyl ring is fixed in an axial orientation relative to thepiperidine ring by the rigid framework of the structure (FIG. 15). The3-hydroxyphenyl ring in the 3,4-dimethyl-4-(3-hydroxyphenyl)piperidineanalogs 4a can be either in axial or equatorial positions (FIG. 15). ¹Hand ¹³C NMR studies^(6,7) as well as molecular modeling studies² suggesta preference for the 3-hydroxyphenyl equatorial conformation.5-(3-Hydroxyphenyl)morphans like 5a-c are sterically constrained4-(3-hydroxyphenyl)piperidines with the 3-hydroxyphenyl ring fixed inthe equatorial position (FIG. 15). The pure antagonist activity of themorphans 5b and 5c strongly suggests that opioid ligands of the phenylpiperidine class express potent opioid antagonist activity with their3-hydroxyphenyl group in an equatorial position.

A comparison of the radioligand and [³⁵S]GTPγS binding properties of theN-substituted 9β-methyl-5-(3-hydroxyphenyl)morphans (5b and 5c) to thoseof the N-substituted 3,4-dimethyl-4-(3-hydroxyphenyl)piperidines (4a and4b) strongly suggests that these two types of compounds are interactingwith opioid receptors in a similar mode. The pure antagonist activity of5b, which is increased when the N-methyl group is replaced by aphenethyl group to give 5c, properties unique to the3,4-dimethyl-4-(3-hydroxyphenyl)piperidine class of antagonist, stronglysupports the hypothesis that this class of opioid antagonist expressespure antagonist activity with the 4-(3-hydroxyphenyl) group in anequatorial conformation.⁸

In summary, 9β-methyl-5-(3-hydroxyphenyl)morphans are a new structuraltype of pure opioid antagonist. The data also strongly supports theproposed 4-(3-hydroxyphenyl) equatorial piperidine chair mode ofinteraction for the trans-3,4-dimethyl-(3-hydroxyphenyl)piperidine classof opioid antagonist.

Experimental Section

Melting points were determined on a Thomas-Hoover capillary tubeapparatus and 5 are not corrected. Elemental analyses were obtained byAtlantic Microlabs, Inc. and are within ±0.4% of the calculated values.¹H-NMR were determined on a Bruker WM-250 spectrometer usingtetramethylsilane as an internal standard. Silica gel 60 (230-400 mesh)was used for all column chromatography. All reactions were followed bythin-layer chromatography using Whatman silica gel 60 TLC plates andwere visualized by UV or by charring using 5% phosphomolybdic acid inethanol. All solvents were reagent grade. Tetrahydrofuran and diethylether were dried over sodium benzophenone ketyl and distilled prior touse.

The [³H]DAMGO, DAMGO, and [³H][D-Ala²,D-Leu⁵]enkephalin were obtainedvia the Research Technology Branch, NIDA, and were prepared by MultiplePeptide Systems (San Diego, Calif.). The [³H]U69,593 and [³⁵S]GTPγS(SA=1250 Ci/mmol) were obtained from DuPont New England Nuclear (Boston,Mass.). U69,593 was obtained from Research Biochemicals International(Natick, Mass.). Levallorphan was a generous gift from Kenner Rice,Ph.D., NIDDK, N1H (Bethesda, Md.). GTPγS and GDP were obtained fromSigma Chemical Company (St. Louis, Mo.). The sources of other reagentsare published.⁸

1,2,3,4-Tetrahydro-4-allyl-1,5-dimethyl-4-(3-methoxyphenyl)pyridine (7).To a solution of 500 mg (2.3 mmol) of1,2,6-trihydro-1,3-dimethyl-4-(3-methoxy)pyridine (6) in 15 mL of THF at−42° C. was added s-BuLi in cyclohexane (1.3M, 2.9 mmol). After 1 h,allyl bromide (2.3 mmol) was added, and the color of the solutionchanged from dark red to yellow. After been stirred for 1 h at −42° C.,the mixture was allowed to warmed to 0° C. and then quenched with water(10 mL). Diethyl ether (10 mL) was added, and the aqueous layer wasextracted with ether (2×). The combined ether layers were washed withwater (10 mL), saturated NaHCO₃, brine, and dried over Na2SO4.Evaporation of solvent afforded 590 mg (˜100%) of crude 7. The crudeproduct was used directly in the next step without further purification.¹H NMR (CDCl₃) δ 7.26 (m, 1H), 7.01 (m, 2H), 6.74 (m, 1H), 5.89 (s, 1H),5.82 (m, 1H), 5.13 (m, 2H), 3.80 (s, 3H), 2.68-2.40 (m, 3H), 2.55 (s,3H), 2.22 (m, 1H), 1.66 (m, 2H), 1.52 (s, 3H). ¹³C NMR (CDCl₃) δ 159.2,151.1, 136.7, 135.8, 128.7, 119.8, 117.4, 114.3, 110.1, 107.7, 55.1,46.1, 43.1, 43.0, 41.7, 36.4, 17.3.

2,9-Dimethyl-5-(3-methoxyphenyl)-2-azabicyclo[3.3.1]non-3-ene (8a,b). Asolution of 300 mg (1.17 mmol) of 7 in 6 mL of 85% H₃PO₄/HCO2H (1:1) wasstirred at room temperature for 72 h. The resulting dark-brown mixturewas diluted with water (6 mL) and cooled in an ice bath while NaOH (25%w/w) was added until pH 8. The aqueous solution was extracted with CHCl₃(3×). The combined organic layers were washed with aqueous NaHCO₃ andbrine and dried over Na₂SO₄. Evaporation of the solvent gave 270 mg(90%) of crude products 5a and 8b in a ratio of 3:1. The crude productswere used directly in the next step without further purification. ¹H NMR(CDCl₃) of the mixture: δ 7.24-6.70 (m, 4H), 6.16 (d, 1H, J=9.2 Hz),4.34 (d, 1H, J=7.0 Hz), 4.13 (d, 1H, J=9.1 Hz), 3.80 (s, 3H), 2.80 (s,3H), 3.10-1.40 (m, 8H), 0.74 (d, 3H, J=8.6 Hz), 0.57 (d, 3H, J=8.1 Hz).

2,9β-Dimethyl-5-(3-methoxyphenyl)-2-azabicyclo[3.3.1]nonane (9). Asolution of 270 mg (1.05 mmol) of 8a and 8b mixture and acetic acid(1.05 mmol, 0.061 mL) in 5 mL of dichloroethane was treated withNaBH(OAc)₃ under N₂ atmosphere. The reaction was stirred at roomtemperature for 2 h. The reaction was quenched by adding 10% NaOH topH˜10. The mixture was extracted with ether (3×), washed with water andbrine. The organic phase was dried over Na₂SO₄ and concentrated underreduced pressure. Isolation of the major isomer by chromatography (1%Et₃N/EtOAc) gave 135 mg (50%) of 9 as a colorless oil. ¹H NMR (CDCl₃) of9 δ 7.26 (m, 1H), 6.94 (m, 2H), 6.70 (m, 1H), 3.80 (s, 3H), 3.05-2.90(m, 2H), 2.71 (m, 1H), 2.43 (s, 3H), 2.42-2.30 (m, 2H), 2.28-2.15 (m,1H), 2.00-1.35 (m, 6H), 0.86 (d, 3H, J=8.25 Hz). ¹³C NMR (CDCl₃) of 9159.2, 152.0, 128.9, 118.0, 112.3, 109.6, 59.7, 55.1, 51.1, 43.1, 42.5,40.0, 38.3, 29.1, 25.6, 23.4, 14.8. Anal. (C₁₇H₂₅NO): C, H, N.

2,9β-Dimethyl-5-(3-hydroxyphenyl)-2-azabicyclo[3.3.1]nonane (5b).Compound 9 was treated with 4 mL of glacial acetic acid and 4 mL of 48%aqueous hydrobromic acid at reflux temperature for 20 h. The reactionwas cooled to room temperature and diluted with 10 mL of water. The pHwas adjusted to 10 by using 50% NaOH with ice cooling. The product wasextracted into a mixture of 3:1 1-butanol/toluene, dried over Na₂SO₄,and concentrated under reduced pressure. Separation by chromatography[50% (80% CHCL₃, 18% MeOH, 2% NH₄OH) in chloroform] provided 199 mg(84%) of 5b as a white solid.

¹H NMR (CDCl₃) δ 7.15 (m, 1H), 6.87-6.75 (m, 2H), 6.61 (m, 1H),3.10-2.90 (m, 2H), 2.77 (m, 1H), 2.44 (s, 3H), 2.50-2.30 (m, 2H),2.25-2.10 (m, 1H), 2.00-1.60 (m, 5H), 1.60-1.40 (m, 1H), 0.80 (d, 3H,J=8.3 Hz). ¹³C NMR (CDCl₃) δ 155.9. The hydrochloride salt was preparedand crystallized from ether/methanol using 1N HCl in ethyl ether. 152.0,129.1, 117.5, 113.0, 112.4, 59.7, 51.0, 43.0, 42.0, 40.2, 38.0, 29.0,25.6, 23.2, 14.6. The structure of this compound was determined bysingle crystal X-ray analysis. Anal. (C₁₆H₂₄ClNO): C, H, N.

5-(3-Hydroxyphenyl)-9β-methyl-2-azabicyclo[3.3.1]nonane (10). A solutionof 200 mg (1.28 mmol) of phenyl chloroformate was added dropwise to 300mg (1.16 mmol) of 9 in 10 mL of dichloromethane at room temperatureunder a nitrogen atmosphere. The reaction was heated to reflux for 6 h.Since the reaction was not complete by TLC, the solvent was then changedto dichloroethane and the reflux was continued for another 12 h. Themixture was cooled to room temperature and concentrated under reducedpressure. The resulting oil was treated with 10 mL of 1N NaOH andstirred with slight warming for 15 min. The product carbamate was thenextracted with ether, and the ether layer was washed with 1N HCl andwater. The organic phase was dried over Na₂SO₄ and concentrated underreduced pressure. The residue was then treated with 5 mL of ethanol and1.5 mL of 50% aqueous KOH at reflux for 70 h. The mixture was cooled andconcentrated under reduced pressure. The resulting concentrate wasextracted with ether (2×), and the ether layers were concentrated invacuo. The resulting oil was dissolved into 10 mL of 1 N HCl and washedwith ether. The aqueous layer was then made strongly basic (pH>12) with50% NaOH with ice cooling. The desired amine was extracted into ether(2×), and the ether extracts were washed, dried over Na₂SO₄, andconcentrated under reduced pressure to give 207 mg (70%) of a lightyellow oil. This was treated with 4 mL of glacial acetic acid and 4 mLof 48% aqueous hydrobromic acid at reflux temperature for 20 h. Thereaction was cooled to room temperature and diluted with 10 mL of water.The pH was adjusted to 10 by using 50% NaOH with ice cooling. Theproduct was extracted into a mixture of 3:1 1-butanol/toluene, driedover Na₂SO₄, and concentrated under reduced pressure to yield 100 mg(51%) of 10 as a semisolid. The crude product 10 was used directly inthe next step without further purification. ¹H NMR (CD₃OD) δ 7.15 (m,1H), 6.79-6.75 (m, 2H), 6.65 (m, 1H), 3.70-3.30 (m, 3H), 2.70 (m, 1H),2.45-1.70 (m, 8H), 0.87 (d, 3H, J=8.3 Hz).

5-(3-Hydroxyphenyl)-9β-methyl-2-(2′-phenylethyl)-2-azabicyclo[3.3.1]nonane(5c). To a solution of 100 mg (0.43 mmol) of 10 and 190 mg (0.43 mmol)of BOP reagent and 0.19 mL (1.38 mmol) of triethylamine in 15 mL of THFwas added phenylacetic acid (70.25 mg, 0.52 mmol). The mixture wasstirred at room temperature for 1 h. The reaction was diluted with 45 mLof water and ether (45 mL). The aqueous layer was extracted with ether(2×). The combined ether layers were washed with NaHCO₃ and brine, anddried over Na₂SO₄. Evaporation of solvent provided the crude product asa colorless oil. The crude amide was dissolved in THF (8 mL). Thesolution was cooled to 0° C., and borane:methyl sulfide complex (0.4 mL,0.8 mmol) was added dropwise. After vigorous reaction ceased, theresulting mixture was slowly heated to reflux and maintained at thattemperature for 4 h. The reaction mixture was cooled to 0° C., 6 mL ofmethanol was added, and the mixture was stirred for 1 h. Anhydroushydrogen chloride in ether (1 mL) was added to attain a pH<2, and theresulting mixture was gently refluxed for 1 h. After the mixture wascooled to room temperature, methanol was added, and the solvents wereremoved on a rotovap. The residue obtained was made basic (pH>12) byadding 25% NaOH and extracted with ether (3×). The combined ether layerswere dried over Na₂SO₄ and concentrated under reduced pressure.Separation by chromatography (1% Et₃N/50% EtOAc/hexanes) gave 38 mg(71%) of amine 5c as a colorless oil. ¹H NMR (CDCl₃) δ 7.30-7.14 (m,6H), 6.85 (m, 2H), 6.63 (m, 1H), 4.71 (br s, 1H), 3.05 (m, 2H), 2.88 (m,1H), 2.79 (s, 4H), 2.43-2.15 (m, 3H), 1.94-1.65 (m, 5H), 1.65-1.45 (m,1H), 0.83 (d, 3 H, J=8.2 Hz). ¹³C NMR (CDCl₃) δ 155.7, 152.5, 140.9,129.1, 128.8, 128.3, 125.9. The hydrochloride salt was prepared andcrystallized from ether/methanol using 1N HCl in ethyl ether. 117.7,113.0, 112.4, 57.4, 57.2, 49.5, 42.4, 40.0, 38.7, 34.1, 29.1, 26.2,23.4, 14.7. Anal. (C₂₃H₃₀ClNO): C, H, N.

Opioid Binding Assays. Mu binding sites were labeled using[³H][D-Ala²-MePhe⁴,Gly-ol⁵]enkephalin ([³H]DAMGO) (2.0 nM, SA=45.5Ci/mmol), and delta binding sites were labeled using[³H][D-Ala²,D-Leu⁵]enkephalin (2.0 nM, SA=47.5 Ci/mmol) using rat brainmembranes prepared as described.⁹ Kappa-1 binding sites were labeledusing [³H]U69,593 (2.0 nM, SA=45.5 Ci/mmol) and guinea pig membranespretreated with BIT and FIT to deplete the mu and delta binding sites.⁸

[³H]DAMGO binding proceeded as follows: 12×75 mm polystyrene test tubeswere prefilled with 100 μL of the test drug which was diluted in bindingbuffer (BB: 10 mM Tris-HCl, pH 7.4, containing 1 mg/mL BSA), followed by50 μL of BB, and 100 μL of [³H]DAMGO in a protease inhibitor cocktail(10 mM Tris-HCl, pH 7.4, which contained bacitracin (1 mg/mL), bestatin(100 μg/mL), leupeptin (40 μg/mL), and chymostatin (20 μg/mL).Incubations were initiated by the addition of 750 μL of the preparedmembrane preparation containing 0.2 mg/mL of protein and proceeded for 4to 6 h at 25° C. The ligand was displaced by 10 concentrations of testdrug, in triplicate, 2×. Nonspecific binding was determined using 20 μMlevallorphan. Under these conditions, the K_(d) of [³H]DAMGO binding was4.35 nM. Brandel cell harvesters were used to filter the samples overWhatman GF/B filters, which were presoaked in wash-buffer (ice-cold 10mM Tris-HCl, pH 7.4).

[³H][D-Ala²,D-Leu⁵]enkephalin binding proceeded as follows: 12×75 mmpolystyrene test tubes were prefilled with 100 μL of the test drug whichwas diluted in BB, followed by 100 μL of a salt solution containingcholine chloride (1 M, final concentration of 100 mM), MnC₁₂ (30 mM,final concentration of 3.0 mM), and, to block mu sites, DAMGO (1000 nM,final concentration of 100 nM), followed by 50 μL of[³H][D-Ala²,D-Leu⁵]enkephalin in the protease inhibitor cocktail.Incubations were initiated by the addition of 750 μL of the preparedmembrane preparation containing 0.41 mg/mL of protein and proceeded for4 to 6 h at 25° C. The ligand was displaced by 10 concentrations of testdrug, in triplicate, 2×. Nonspecific binding was determined using 20 μMlevallorphan. Under these conditions the K_(d) of[³H][D-Ala²,D-Leu⁵]enkephalin binding was 2.95 nM. Brandel cellharvesters were used to filter the samples over Whatman GF/B filters,which were presoaked in wash buffer (ice-cold 1.0 mM Tris-HCl, pH 7.4).

[³H]U69,593 binding proceeded as follows: 12×75 mm polystyrene testtubes were prefilled with 100 μL of the test drug which was diluted inBB, followed by 50 μL of BB, followed by 100 μL of [³H]U69,593 in thestandard protease inhibitor cocktail with the addition of captopril (1mg/mL in 0.1N acetic acid containing 10 mM 2-mercapto-ethanol to give afinal concentration of 1 μg/mL). Incubations were initiated by theaddition of 750 μL of the prepared membrane preparation containing 0.4mg/mL of protein and proceeded for 4 to 6 h at 25° C. The ligand wasdisplaced by 10 concentrations of test drug, in triplicate, 2×.Nonspecific binding was determined using 1 μM U69,593. Under theseconditions the K_(d) of [³H]U69,593 binding was 3.75 nM. Brandel cellharvesters were used to filter the samples over Whatman GF/B filters,which were presoaked in wash buffer (ice-cold 10 mM Tris-HCl, pH 7.4)containing 1% PEI.

For all three assays, the filtration step proceeded as follows: 4 mL ofthe wash buffer was added to the tubes, rapidly filtered and wasfollowed by two additional wash cycles. The tritium retained on thefilters was counted, after an overnight extraction into ICN Cytoscintcocktail, in a Taurus beta counter at 44% efficiency.

³⁵S-GTPγS Binding Assay. Ten frozen guinea pig brains (HarlanBioproducts for Science, Inc, Indianapolis, Ind.) were thawed, and thecaudate putamen were dissected and homogenized in buffer A (3mL/caudate) (Buffer A=10 mM Tris-HCl, pH 7.4 at 4° C. containing 4 μg/mLleupeptin, 2 μg/mL chymostatin, 10 μg/mL bestatin, and 100 μg/mLbacitracin) using a polytron (Brinkman) at setting 6 until a uniformsuspension was achieved. The homogenate was centrifuged at 30,000×g for10 min at 4° C. and the supernatant discarded. The membrane pellets werewashed by resuspension and centrifugation twice more with fresh bufferA, aliquotted into microfuge tubes, and centrifuged in a Tomyrefrigerated microfuge (model MTX 150) at maximum speed for 10 min. Thesupernatants were discarded, and the pellets were stored at −80° C.until assayed.

For the [³⁵S]GTPγS binding assay, all drug dilutions were made up inbuffer B [50 mM TRIS-HCl, pH 7.7/0.1% BSA]. Briefly, 12×75 mmpolystyrene test tubes received the following additions: (a) 50 μLbuffer B with or without an agonist, (b) 50 μL buffer B with or without60 μM GTPγS for nonspecific binding, (c) 50 μL buffer B with or withoutan antagonist, (d) 50 μL salt solution which contained in buffer B 0.3nM [³⁵S]GTPγS, 600 mM NaCl, 600 μM GDP, 6 mM dithiothreitol, 30 mMMgCl₂, and 6 mM EDTA, and (e) 100 μL membranes in buffer B to give afinal concentration of 10 μg per tube. The final concentration of thereagents were 100 mM NaCl, 5 mM MgCl₂, 1 mM EDTA, 1 mM dithiothreitol,100 μM GDP, 0.1% BSA, 0.05-0.1 nM [³⁵S]GTPγS, 500 nM or 10 μM agonists,and varying concentrations (at least 10 different concentrations) ofantagonists. The reaction was initiated by the addition of membranes andterminated after 4 h by addition of 3 mL ice-cold (4° C.) purified water(Milli-Q uv-Plus, Millipore) followed by rapid vacuum filtration throughWhatman GF/B filters presoaked in purified water. The filters were thenwashed once with 5 mL ice-cold water. Bound radioactivity was counted byliquid scintillation spectroscopy using a Taurus (Micromedic) liquidscintillation counter at 98% efficiency after an overnight extraction in5 mL Cytoscint scintillation fluid. Nonspecific binding was determinedin the presence of 10 μM GTPγS. Assays were performed in triplicate, andeach experiment was performed at least 3×.

Data Analysis. The data of the two separate experiments (opioid bindingassays) or three experiments ([³⁵S]-GTPγS assay) were pooled and fit,using the nonlinear least-squares curve-fitting language MLAB-PC(Civilized Software, Bethesda, Md.), to the two-parameter logisticequation¹⁰ for the best-fit estimates of the IC₅₀ and slope factor. TheK_(i) values were then determined using the equation:IC₅₀/1+([L]/K_(d)).

Single-Crystal X-Ray Analysis of 5b. Crystals of 5b were grown fromethyl ether/methanol. Data were collected on a computer-controlledautomatic diffractometer, Siemens P4, with a graphite monochromator onthe incident beam. Data were corrected for Lorentz and polarizationeffects, and a face-indexed absorption correction was applied. Thestructure was solved by direct methods with the aid of program SHELXS¹¹and refined by full-matrix least-squares on F2 values using programSHELXL.¹¹ The parameters refined included the coordinates andanisotropic thermal parameters for all nonhydrogen atoms. Hydrogen atomson carbons were included using a riding model in which the coordinateshifts of their covalently bonded atoms were applied to the attachedhyrdogens with C—H=0.96 Å. H angles were idealized and Uiso(H) set atfixed ratios of Uiso values of bonded atoms. Coordinates were refinedfor H atoms bonded to nitrogen and oxygen. Additional experimental andstructural analysis including an ORTEP figure, tables of atomiccoordinates, bond lengths, and angles are available as supplementarymaterial. Atomic coordinates are also available from the CambridgeCrystallographic Data Centre (Cambridge University Chemical Laboratory,Cambridge CB2 1EW, UK).

References

(1) Evans, D. A.; Mitch, C. H.; Thomas, R. C.; Zimmerman, D. M.; Robey,R. L. Application of metalated enamines to alkaloid synthesis. Anexpedient approach to the synthesis of morphine-based analgesics. J. Am.Chem. Soc. 1980, 102, 5955-5956. WARNING: read the backgroundinformation relating to analogs of MPTP including refferences forZimmerman et al., J. Med. Chem. 1986, 29, 1517-1520 and references citedin reference 2.

(2) Zimmerman, D. M.; Leander, J. D.; Cantrell, B. E.; Reel, J. K.;Snoddy, J.; Mendelsohn, L. G.; Johnson, B. G.; Mitch, C. H.Structure-activity relationships of thetrans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine antagonists for μ and κopioid receptors. J. Med. Chem. 1993, 36(20), 2833-2841.

(3) Thomas, J. B.; Mascarella, S. W.; Rothman, R. B.; Partilla, J. S.;Xu, H.; McCullough, K. B.; Dersch, C. M.; Cantrell, B. E.; Zimmerman, D.M.; Carroll, F. I. Investigation of the N-substituent conformationgoverning potency and μ receptor subtype-selectivity in(+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonists. JMed. Chem. 1998, 41(11), 1980-1990.

(4) Xu, H.; Lu, Y.-F.; Partilla, J. S.; Brine, G. A.; Carroll, F. I.;Rice, K. C.; Lai, J.; Porreca, F.; Rothman, R. B. Opioid peptidereceptor studies. 6. The 3-methylfentanyl congeners RTI-4614-4 and itsenantiomers differ in efficacy, potency, and intrinsic efficacy asmeasured by stimulation of [³⁵S]GTP-γ-S binding using cloned μ-opioidreceptors. Analgesia 1997, 3, 35-42.

(5) Aldrich, J. V. Analgesics. In Burger's Medicinal Chemistry and DrugDiscovery, Wolff, M. E. Eds.; John Wiley & Sons, Inc.: 1996; Vol. 3:Therapeutic Agents.

(6) Casy, A. F.; Dewar, G. H.; Al-Deeb, O. A. A. Stereochemicalinfluences upon the opioid ligand activities of 4-alkyl-4-arylpiperidinederivatives. Chirality 1989, 1, 202-208.

(7) Casy, A. F.; Dewar, G. H.; Al-Deeb, O. A. A. Stereochemical studiesof the 4-alkyl-4-arylpiperidine class of opioid ligand. Magn. Reson.Chem. 1989, 27, 964-972.

(8) Rothman, R. B.; Bykov, V.; de Costa, B. R.; Jacobson, A. E.; Rice,K. C.; Brady, L. S. Interaction of endogenous opioid peptides and otherdrugs with four kappa opioid binding sites in guinea pig brain. Peptides1990, 11, 311-331.

(9) Rothman, R. B.; Xu, H.; Seggel, M.; Jacobson, A. E.; Rice, K. C.;Brine, G. A.; Carroll, F. I. RTI-4614-4: an analog of(+)-cis-3-methylfentanyl with a 27,000-fold binding selectivity for muversus delta opioid binding sites. Life Sci. 1991, 48, PL111-PL-116.

(10) Rodbard, D.; Lenox, R. H.; Wray, H. L.; Ramseth, D. Statisticalcharacterization of the random errors in the radioimmunoassaydose-response variable. Clin. Chem. 1976, 22, 350-358.

(11) SHELXTL-Plus, Release 5.03, Sheldrick, G. M., Siemens AnalyticalX-ray Instruments, Inc., Madison, Wis., 1995.

TABLE 9 Radioligand Binding Results at the Mu, Delta, and Kappa OpioidReceptors for N-Methyl- and N-Phenethyl-9β-methyl-5-(3-hydroxyphenyl)morphans Ki (nM ± SD) μ δ κ Compd [³H]DAMGO^(a) [³H]DADLE^(b)[³H]U69,593^(c) 5b 166 ± 15  >10,000 816 ± 66 5c 3.11 ± 0.21 272 ± 30 14.5 ± 0.99 1b, naltrexone 1.39 ± 0.40 94.9 ± 6.6 4.71 ± 0.7^(a)[³H]DAMGO [(D-Ala²,MePhe⁴,Gly-ol⁵)enkephalin]. Tritiated ligandselective for mu opioid receptor. ^(b)[³H]DADLE[(D-Ala²,D-Leu⁵)enkephalin]. Tritiated ligand selective for delta opioidreceptor. ^(c)[³H]U69,593{[³H](5α,7α,8β)-(−)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec-8-yl]benzeneacetamide}.Tritiated ligand selective for kappa opioid receptor.

TABLE 10 Affinities of theN-Substituted-3,4-dimethyl-(3′-hydroxyphenyl)piperidine Antagonists forthe Mu and Kappa Opioid Receptors^(a) Ki (nM) μ κ Compd [³H]Nal^(b)[³H]EKC^(c) 4a 80 833 4b 1.5 52 1b, naltrexone 0.56 3.9 ^(a)Data takenfrom reference 2. ^(b)[³H]Naloxone (μ receptor assay).^(c)[³H]Ethylketocyclazocine (κ receptor assay).

TABLE 11 Inhibition by Antagonists of [³⁵S]GTPγS Binding in Guinea PigCaudate Stimulated by DAMGO (mu), SNC80 (delta), and U69,593 (kappa)Selective Opioid Agonists^(a) Ki (nM ± SD) μ δ κ Compd (DAMGO)^(a)(SNC80)^(b) (U69,593)^(c) 5b 21.2 ± 2.30  750 ± 85.9  105 ± 10.9 5c0.338 ± 0.028 12.6 ± 1.01  1.34 ± 0.084 1b, naltrexone 0.930 ± 0.21 19.3 ± 2.25 2.05 ± 0.21 ^(a)DAMGO [(D-Ala²,MePhe⁴,Gly-ol⁵)enkephalin].Agonist selective for mu opioid receptor. ^(b)SNC-80([(+)-4-[(αR)-α-(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide).Agonist selective for delta opioid receptor. Agonist selective for deltaopioid receptor. ^(c)U69,593(trans-3,4-dichloro-N-methyl[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide).Agonist selective for kappa opioid receptor.

Calcd. Found Compd C H N C H N 9 C₁₇H₂₅NO 78.72 9.71 5.40 78.79 9.755.34 5b C₁₆H₂₄ClNO 68.19 8.53 4.91 68.25 8.53 5.03 5c C₂₃H₃₀ClNO 74.278.13 3.77 74.16 8.12 3.71

TABLE S1 Crystal data and structure refinement for 5b. Empirical formulaC₁₆ H₂₄ Cl N O Formula weight 281.81 Temperature 293(2)K Wavelength1.54178 Å Crystal system Monoclinic Space group P2(1)/c Unit celldimensions a = 14.183(1) Å α = 90°. b = 9.996(1) Å β = 90.33(2)°. c =11.126(1) Å γ = 90°. Volume 1577.5(2) Å³ Z 4 Density (calculated) 1.187Mg/m³ Absorption coefficient 2.072 mm⁻¹ F(000) 608 Crystal size 0.40 ×0.26 × 0.24 mm³ Theta range for data collection 3.12 to 57.49°. Indexranges −15 <= h <= 3, −10 <= k <= 1, −12 <= I <= 12 Reflectionscollected 2651 Independent reflections 2154 [R(int) = 0.0312] Absorptioncorrection Integration Max. and min. transmission 0.6449 and 0.5284Refinement method Full-matrix least-squares on F²Data/restraints/parameters 2153/0/180 Goodness-of-fit on F² 1.047 FinalR indices [I > 2sigma(I)] R1 = 0.0472, wR2 = 0.1367 R indices (all data)R1 = 0.0598, wR2 = 0.1493 Largest diff. peak and hole 0.213 and −0.228e.Å⁻³

TABLE S2 Atomic coordinates (×10⁴) and equivalent isotropic displacementparameters (Å² × 10³) for 5b. U(eq) is defined as one third of the traceof the orthogonalized U⁴ tensor. x y z U(eq) Cl(1) 6176(1) 534(1)8837(1) 56(1) C(1) 6136(2) −4826(3) 7545(2) 44(1) N(2) 6354(2) −5819(2)6563(2) 45(1) C(2) 5733(3) −7019(3) 6587(3) 64(1) C(3) 7374(2) −6184(3)6510(3) 54(1) C(4) 8010(2) −4963(3) 6522(3) 49(1) C(5) 7760(2) −3857(3)7430(2) 40(1) C(6) 7948(2) −4300(3) 8752(2) 48(1) C(7) 7345(2) −5466(3)9198(3) 58(1) C(8) 6319(2) −5367(3) 8813(2) 56(1) C(9) 6690(2) −3545(2)7321(2) 39(1) C(9A) 6394(2) −2839(3) 6157(2) 48(1) C(10) 8344(2)−2595(3) 7206(2) 43(1) C(11) 8071(2) −1398(3) 7730(3) 49(1) O(12)8256(2) 962(2) 8052(3) 79(1) C(12) 8549(2) −214(3) 7554(3) 56(1) C(13)9351(2) −206(4) 6853(3) 68(1) C(14) 9646(2) −1386(4) 6351(3) 72(1) C(15)9160(2) −2568(3) 6503(3) 60(1)

TABLE S3 Bond lengths [Å] and angles [°] for 5b. C(1)-N(2) 1.509(3)C(1)-C(9) 1.524(4) C(1)-C(8) 1.532(4) N(2)-C(2) 1.488(4) N(2)-C(3)1.494(4) C(3)-C(4) 1.517(4) C(4)-C(5) 1.540(4) C(5)-C(10) 1.530(4)C(5)-C(9) 1.553(3) C(5)-C(6) 1.558(4) C(6)-C(7) 1.530(4) C(7)-C(8)1.518(4) C(9)-C(9A) 1.533(3) C(10)-C(11) 1.387(4) C(10)-C(15) 1.401(4)C(11)-C(12) 1.378(4) O(12)-C(12) 1.365(4) C(12)-C(13) 1.383(5)C(13)-C(14) 1.371(5) C(14)-C(15) 1.379(5) N(2)-C(1)-C(9) 109.1(2)N(2)-C(1)-C(8) 113.6(2) C(9)-C(1)-C(8) 111.2(2) C(2)-N(2)-C(3) 112.2(2)C(2)-N(2)-C(1) 113.1(2) C(3)-N(2)-C(1) 113.1(2) N(2)-C(3)-C(4) 112.3(2)C(3)-C(4)-C(5) 116.4(2) C(10)-C(5)-C(4) 111.0(2) C(10)-C(5)-C(9)110.5(2) C(4)-C(5)-C(9) 108.8(2) C(10)-C(5)-C(6) 107.4(2) C(4)-C(5)-C(6)112.1(2) C(9)-C(5)-C(6) 107.0(2) C(7)-C(6)-C(5) 115.5(2) C(8)-C(7)-C(6)113.3(2) C(7)-C(8)-C(1) 116.1(2) C(1)-C(9)-C(9A) 112.7(2) C(1)-C(9)-C(5)108.9(2) C(9A)-C(9)-C(5) 114.9(2) C(11)-C(10)-C(15) 116.8(3)C(11)-C(10)-C(5) 119.4(2) C(15)-C(10)-C(5) 123.8(2) C(12)-C(11)-C(10)122.9(3) O(12)-C(12)-C(11) 122.1(3) O(12)-C(12)-C(13) 118.5(3)C(11)-C(12)-C(13) 119.4(3) C(14)-C(13)-C(12) 118.6(3) C(13)C(14)-C(15)122.2(3) C(14)-C(15)-C(10) 120.0(3)

TABLE S4 Anisotropic displacement parameters (Å² × 10³)for 5b. Theanisotropic displacement factor exponent takes the form: −2π²[h²a*²U¹¹ +... + 2 h k a* b* U¹²] U¹¹ U²² U³³ U²³ U¹³ U¹² Cl(1) 62(1) 59(1) 48(1)3(1) −5(1) 10(1) C(1) 47(2) 39(2) 45(2) 1(1) −1(1) −1(1) N(2) 58(2)34(1) 43(1) 3(1) −7(1) −4(1) C(2) 88(2) 42(2) 62(2) 5(2) −8(2) −21(2)C(3) 67(2) 44(2) 52(2) −7(1) −4(1) 11(2) C(4) 52(2) 47(2) 50(2) −7(1)−1(1) 9(1) C(5) 41(1) 36(1) 42(1) −2(1) −2(1) 5(1) C(6) 50(2) 48(2)45(2) −1(1) −9(1) 7(1) C(7) 8O(2) 51(2) 43(2) 8(1) −8(2) −2(2) C(8)70(2) 53(2) 45(2) 4(1) 4(1) −16(2) C(9) 39(1) 35(1) 42(1) 0(1) −1(1)−1(1) C(9A) 50(2) 40(2) 56(2) 6(1) −8(1) 1(1) C(10) 36(1) 48(2) 45(2)2(1) −2(1) −2(1) C(11) 41(2) 44(2) 62(2) −3(1) 4(1) −4(1) O(12) 73(2)40(1) 124(2) −6(1) 8(2) −10(1) C(12) 48(2) 49(2) 69(2) 2(2) −8(2) −8(1)C(13) 54(2) 65(2) 85(2) 7(2) −2(2) −22(2) C(14) 44(2) 92(3) 83(2) −1(2)14(2) −19(2) C(15) 45(2) 68(2) 68(2) −9(2) 5(2) −2(2)

TABLE S5 Hydrogen coordinates (×10⁴) and isotropic displacementparameters (Å² × 10³) for 5b. x y z U(eq) H(1A) 5464(2) −4606(3) 7484(2)52 H(2) 6227(18) −5389(28) 5805(27) 48(8) H(2A) 5086(3) −6741(3) 6621(3)97 H(2B) 5881(3) −7550(3) 7282(3) 97 H(2C) 5832(3) −7540(3) 5874(3) 97H(3A) 7489(2) −6694(3) 5783(3) 65 H(3B) 7531(2) −6749(3) 7191(3) 65H(4A) 8004(2) −4574(3) 5723(3) 59 H(4B) 8649(2) −5258(3) 6687(3) 59H(6A) 8607(2) −4549(3) 8829(2) 57 H(6B) 7843(2) −3538(3) 9274(2) 57H(7A) 7605(2) −6297(3) 8894(3) 70 H(7B) 7378(2) −5497(3) 10069(3) 70H(8A) 5994(2) −4795(3) 9381(2) 67 H(8B) 6040(2) −6250(3) 8870(2) 67H(9A) 6538(2) −2934(2) 7981(2) 46 H(9AA) 6762(2) −2041(3) 6057(2) 73H(9AB) 5738(2) −2608(3) 6196(2) 73 H(9AC) 6496(2) −3425(3) 5487(2) 73H(11A) 7544(2) −1394(3) 8222(3) 59 H(12) 7646(36) 906(46) 8364(40)110(15) H(13A) 9683(2) 583(4) 6724(3) 82 H(14A) 10192(2) −1389(4)5893(3) 87 H(15A) 9374(2) −3347(3) 6139(3) 72

This Example is described in Thomas et al, J. Med. Chem., V. 41, No. 21,4143-4149 (1998) incorporated herein by reference, inclusive of the“Supporting Information Available” described at p. 4149.

Example 5 Synthesis of 9β-Methyl-2-alkyl-7-oxo-5-arylmorphans

Summary

A convergent synthetic approach to9β-methyl-2-alkyl-7-oxo-5-arylmorphans has been developed utilizingalkylation of the metalloenamine of1,2,3,6-tetrahydro-4-aryl-1-alkylpyridines with2-(chloromethyl)-3,5-dioxahex-1-ene (Okahara's reagent).

Chemistry

Thus, treatment of the lithium salt of 15a with 18 provided 16a (notisolated) which cyclized on acidification with hydrochloric acid intetrahydrofuran to give a 10:1 mixture of 17a and 17d as determined by¹H NMR analysis (FIG. 16). Separation by silica gel chromatographyprovided 43% of 17a. Proton assignments were made using a combination ofHMQC, HMBC, and COSY. The 9β stereochemical assignments for 17a weremade using NOESY techniques. In particular, the axial 9β-methyl groupwas observed to show an NOE interaction with the 4β proton.¹

To expand this method to the ring unsubstituted derivatives and toexplore potential limitations of the chemistry, compounds 17b (47%) and17c (42%) were also prepared. It was shown earlier that differences inreactivities exist between unsubstituted and substituted systems, 15b,cand 15a. For example, s-BuLi is needed to effectively deprotonate 15a asopposed to 15b and 15c which require only n-BuLi.² This is a convenientroute to the 7-oxo-phenylmorphan derivatives from either substituted orunsubstituted 4-phenyl-1,2,3,6-tetrahydropyridines from intermediateswhich can be prepared in bulk and stored for long periods of time.

In summary, the 9β-methyl-7-oxo-5-arylmorphan 17a can be prepared in aconvergent manner from tetrahydropyridine 15a by alkylation with2-(chloromethyl)-3,5-dioxahex-1-ene 18 followed by cyclization underacidic conditions. This method provides the first reported access to the9β-methyl substituted system with good control of the stereochemistry.Application of the method to 15b and 15c provides a higher yieldingroute to the unsubstituted 7-oxo-phenylmorphan ring system and isamenable to large-scale synthesis.

References and Notes

1. ¹H NMR (CDCl₃) δ 0.92 (d, 3H, 9-CH₃), 1.76 (d, 1H, H4α), 2.23 (dd,1H, H8), 2.33 (s, 3H, NCH₃), 2.37 (dd, 1H, H4β), 2.38 (dd, 1H, H3), 2.43(d, 1H, H6), 2.50 (q, 1H, H9), 2.62 (d, 1H, H6), 2.72 (m, 1H, H3), 2.97(d, 1H, H8), 3.10 (m, 1H, H1), 3.78 (s, 3H, OCH₃), 6.75 (dd, 1H, ArH),6.87 (s, 1H, ArH), 6.92 (d, 1H, ArH), 7.25 (dd, 1H, ArH).

2. Barnett, C. J.; Copley-Merriman, C. R.; Maki, J. J. Org. Chem. 1989,54, 4795-4800.

Supplementary Information

Melting points were determined on a Thomas-Hoover capillary tubeapparatus and are not corrected. Elemental analyses were obtained byAtlantic Microlabs, Inc. and are within ±0.4% of the calculated values.¹H-NMR spectra were determined on a Bruker WM-250 spectrometer usingtetramethylsilane as an internal standard. Radial chromatography wasperformed on a Harrison Research Chromatron model 7924T. All reactionswere followed by tin-layer chromatography using Whatman silica gel 60TLC plates and were visualized by WV or by charring using 5%phosphomolybdic acid in ethanol or by iodine staining. All solvents werereagent grade. In reactions, tetrahydrofuran and diethyl ether weredried over sodium benzophenone ketyl and distilled prior to use.

Note: The choice of piperidone in this synthesis is important in orderto avoid the production of neurotoxic tetrahydropyridines such as1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). It has beendemonstrated that the neurotoxic properties associated with MPTP orm-methoxy-MPTP are eliminated by any one of the following:

N-substituents larger than methyl, piperidine ring substitution, and/oraryl substituents larger than methoxy.¹⁻³

2,9-Dimethyl-5-(3-methoxyphenyl)-2-azabicyclo[3.3.1]nonan-7-one (17a):To a solution of 1500 mg (6.9 mmol) of tetrahydropyridine 15a⁴ and TMEDA(2.1 mL, 13.8 mmol) in 30 mL of THF at −42° C. was added s-BuLi incyclohexane (1.3 M, 8.9 mmol). After 1 h,2-(chloromethyl)-3,5-dioxa-1-hexene 18 (1.32 g, 9.7 mmol) was added, andthe color of the solution changed slowly from dark red to yellow. Afterbeing stirred for 1 h at −42° C. and kept 3 h at −23° C., the mixturewas allowed to warm to 0° C. and then quenched with 1N HCl (20 mL).Diethyl ether (20 mL) was added, and the aqueous layer was extractedwith ether (2×). The aqueous layer was adjusted to pH 10 and extractedwith diethyl ether (3×). The combined ether layers were washed withwater (10 mL), saturated NaHCO₃, brine, and dried over Na₂SO₄.Evaporation of solvent afforded 1.31 g (˜60%) of crude 16a. The crudeproduct was used directly in the next step without further purification.¹H NMR (CDCl₃) δ 7.27 (t, 1H, J=9.6 Hz), 7.02 (m, 2H), 6.72 (m, 1H),5.83 (s, 1H), 4.93 (s, 2H), 3.81 (s, 3H), 3.43 (s, 3H), 2.70-2.40 (m,8H), 2.52 (s, 3H), 1.61 (s, 3H). A solution of 500 mg of 16a in 3 mL of6 M HCl and 25 mL of THF was stirred at room temperature for 72 h. Theresulting brown mixture was neutralized with 10% NaOH (10 mL) untilpH>9. The aqueous solution was extracted with diethyl ether (3×). Thecombined organic layers were washed with aqueous NaHCO₃ and brine. Theorganic phase was dried over Na₂SO₄ and concentrated under reducedpressure. The NMR shows that the ratio of 17a to 17d is about 10:1.Separation by chromatography [10% (80% chloroform, 18% methanol, 2%NH₄OH)/chloroform] gave 310 mg of 17a as a colorless oil (43% from 15a).¹H NMR (CDCl₃) δ 7.28 (t, 1H, J=9.5 Hz), 6.93 (m, 1H), 6.86 (m, 1H),6.76 (dd, 1H, J=2.2, 9.7 Hz), 3.81 (s, 3H), 3.13 (m, 1H), 3.0 (d, 1H,J=20.5 Hz), 2.76 (m, 1H), 2.66-2.17 (m, 6H), 2.36 (s, 3H), 1.76 (m, 1H),0.93 (d, 3H, J=8.2 Hz). ¹³C NMR (CDCl₃) 210.5, 159.6, 148.7, 129.4,117.6, 112.2, 110.3, 61.7, 55.9, 55.0, 47.1, 42.8, 41.4, 39.6, 29.5,13.8. Anal. Calcd. for C₁₇H₂₃NO₂: Found: C, 76.72; H, 8.62, N, 5.23.

2-Ethyl-5-(3-methoxyphenyl)-2-azabicyclo[3.3.1]nonan-7-one (17b): To asolution of 500 mg (2.3 mmol) of tetrahydropyridine 15b [1] andtetramethylethylene diamine (TMEDA) (0.69 mL, 4.6 mmol) in 15 mL of THFat −42° C. was added n-BuLi in hexanes (2.5M, 2.9 mmol). After 1 h,2-(chloromethyl)-3,5-dioxa-1-hexene 18 (440 mg, 3.2 mmol) was added, andthe color of the solution changed slowly from dark red to yellow. Afterbeing stirred for 1 h at −42° C. and kept 3 h at −23° C., the mixturewas allowed to warm to 0° C. and then quenched with 1N HCl (10 mL).Diethyl ether (10 mL) was added, and the aqueous layer was extractedwith ether (2×). The aqueous layer was adjusted to pH 10 and extractedwith diethyl ether (3×). The combined ether layers were washed withwater (10 mL), saturated NaHCO₃, brine, and dried over Na₂SO₄.Evaporation of solvent afforded 510 mg (70%) of crude 16b. The crudeproduct was used directly in the next step without further purification.¹H NMR (CDCl₃) δ 7.20 (t, 1H, J=9.1 Hz), 6.97 (m, 2H), 6.67 (dd, 1H,J=1.9, 8.4 Hz), 6.03 (d, 1H, J=9.8 Hz), 4.74 (s, 2H), 4.69 (d, 1H, J=9.6Hz), 3.79 (s, 3H), 3.26 (s, 3H), 2.86 (q, 2H, J=8.6 Hz), 2.80-2.39 (m,6H), 2.12 (m, 2H), 1.02 (t, 3H, J=8.6 Hz). A solution of 510 mg of 16bin 3 mL of 6 M HCl and 25 mL of THF was stirred at room temperature for72 h. The resulting brown mixture was neutralized with 10% NaOH (10 mL)until pH>9. The aqueous solution was extracted with diethyl ether (3×).The combined organic layers were washed with aqueous NaHCO₃ and brine.The organic phase was dried over Na₂SO₄ and concentrated under reducedpressure. Separation by chromatography [10% (80% chloroform, 18%methanol, 2% NH₄OH)/chloroform] gave 352 mg (80%, 47% from 15b) of 17bas colorless oil. ¹H NMR (CDCl₃) δ 7.28 (t, 1H, J=9.6 Hz), 6.92 (m, 2H),6.78 (dd, 1H, J=3.0, 9.7 Hz), 3.81 (s, 3H), 3.60 (m, 1H), 2.82 (m, 3H),2.55 (q, 2H, J=8.6 Hz), 2.44-1.92 (m, 7H), 1.10 (t, 3H, J=8.6 Hz). ¹³CNMR (CDCl₃) 209.4, 158.7, 149.0, 128.5, 115.9, 110.2, 110.0, 54.1, 52.4,52.2, 47.4, 44.4, 38.2, 37.6, 37.1, 36.7, 12.7. Anal. Calcd. forC₁₇H₂₃NO₂: C, 74.69; H, 8.48; N, 5.12. Found: C, 74.78; H, 8.60; N,5.24.

2-Benzyl-5(3-methoxyphenyl)-2-azabicyclo[3.3.1]nonan-7-one (17c):3-Bromoanisole (50.0 g, 0.264 mol) was dissolved in 150 mL of THF andthen chilled to −78° C. n-Butyllithium (1.6M, 175 mL, 0.276 mol) wasthen added while maintaining the reaction temperature at −70° C. orbelow. After complete addition, the reaction mixture was stirred for anadditional 60 min. 1-Benzyl-4-piperidone in 150 mL of THF was then addedat such a rate as to maintain the reaction temperature at −70° C. orbelow. The reaction was stirred at −70° C. for an additional 15 min,then the dry ice-acetone bath was removed, and the reaction was allowedto come to room temperature. Brine (400 mL) was added, and the organiclayer was separated and washed with an additional 300 mL of brine. Theorganic layer was separated, dried (K₂CO₃), and concentrated in vacuo.6N HCl (250 mL) was added to the oily residue which was then washed withEtOAc. The aqueous layer was separated, basified with 50% NaOH, andextracted with EtOAc. The EtOAc layer was separated, dried (K₂CO₃), andconcentrated in vacuo to give 75.7 g of4-(3-methoxyphenyl)-1-benzyl-4-piperidinol as an orange oil. A samplewas chromatographed on silica gel using hexane/EtOAc (7:3) mixtures asthe eluent to afford a yellow oil which was dissolved in ether andtreated with ethereal hydrochloric acid to give4-(3-methoxyphenyl)-1-benzyl-4-piperidinol hydrochloride as a whitesolid (mp 195-197° C.). ¹H NMR (CDCl₃) (free base) δ (ppm) 1.64-1.75 (m,2H), 2.09-2.21 (m, 2H), 2.41-2.51 (m, 2H), 2.71-2.80 (m, 2H), 3.51 (s,2H), 3.80 (s, 3H), 6.77-6.81 (m, 1H), 7.06-7.09 (m, 2H), 7.23-7.35 (m,6H). Anal. Calcd for C₁₉H₂₃NO₂ HCl.½H₂O: C, 66.56; H, 7.06; N, 4.09.Found: C, 66.41; H, 7.31; N, 4.33.

This material, 4-(3-methoxyphenyl)-1-benzyl-4-piperidinol (75.7 g, 0.25mol), was dissolved in 400 mL of toluene, tosic acid (101.4 g, 0.53 mol)was added, and the mixture was heated under reflux in a Dean Stark trapfor 90 min. The reaction mixture was cooled to room temperature, andwater (400 mL) was added. The bottom layers were separated, made basicwith 5N NaOH, and extracted with EtOAc. The EtOAc layer was separated,washed with brine, dried (K₂CO₃), and concentrated in vacuo to give 73.0g of a red-orange oil. The oil was chromatographed on silica gel usinghexane/EtOAc (4:1) mixtures as the eluent to afford 54.2 g of1,2,3,6-tetrahydro-4-(3-methoxyphenyl)-1-benzylpyridine 15c (78%) as anorange oil. A sample of the free base was converted to its hydrochloridesalt (ethereal HCl) to give1,2,3,6-tetrahydro-4(3-methoxyphenyl)-1-benzylpyridine hydrochloride asa white solid (mp 196-196° C). ¹H NMR (CDCl₃) (free base) δ (ppm)2.54-2.57 (br m, 2H), 2.68-2.73 (m, 2H), 3.14-3.18 (m, 2H), 3.63 (s,2H), 3.78 (s, 3H), 6.04-6.07 (m, 1H), 6.79 (dd, 1H), 6.91-7.00 (m, 2H),7.19-7.39 (m, 6H). Anal. Calcd. for C₁₉H₂₁NO.HCl.¼H₂O: C, 71.46; H,6.79; N, 4.39. Found: C, 71.63; H, 6.97; N, 4.42.

1,2,3,6-Tetrahydro-4-(3-methoxyphenyl)-1-benzylpyridine 15c (5.0 g,0.018 mol) was dissolved in 70 mL of THF and chilled to −78° C. in a dryice-acetone bath. N-Butyllithium (1.6M, 12.0 mL, 0.0193 mol) was addedto the reaction mixture at a rate that would maintain the temperature at−70° C. or below. After complete addition, the reaction was stirred foran additional 15 min, and the dry ice bath was replaced with a salt-icebath. When the temperature rose to −15° C.,2-(chloromethyl)-3,5-dioxahex-1-ene 18 (3.2 g, 0.023 mol) in 40 mL ofTHF was added while keeping the reaction temperature at −10° C. or belowand stirring for an additional 15 min at −15° C. The bath was removed,and the reaction was stirred at room temperature for an additional 17 h.The reaction was quenched with 30 mL of brine, the organic layer wasseparated, washed with 2×100 mL of brine, separated, dried (K₂CO₃), andconcentrated in vacuo to get 6.8 g of an orange oil. This was dissolvedin 100 mL of THF, and 20 mL of 6N HCl was added. This reaction wasstirred at room temperature overnight. The reaction mixture wasneutralized with aqueous NaHCO₃, added 100 mL of EtOAc, and separatedthe organic layer. The organic layer was washed with 10% NaHCO₃, brine,then separated, dried(K₂CO₃), and concentrated in vacuo to give 4.8 g of17c as a red oil. The oil was chromatographed on silica gel usinghexane/EtOAc (65:35) mixtures, as the eluent, to yield an oil whichcrystallized upon addition of ether to give 2.5 g (42%) of5-(3-methoxyphenyl)-2-benzyl-2-azabicyclo[3.3.1]nonan-7-one 17c as abeige solid (mp 108-109° C.). ¹H NMR (CDCl₃) δ (ppm) 1.88-1.91 (m, 2H),2.12-2.21 (m, 2H), 2.31-2.49 (m, 3H), 2.75-2.99 (m, 3H), 3.49 (br m,1H), 3.60-3.72 (q, 2H), 3.80 (s, 3H), 6.75-6.80 (m, 1H), 6.88-6.96 (m,2H), 7.25-7.34 (m, 6H). ¹³C NMR (CDCl₃) δ 210.4, 159.8, 150.2, 138.7,129.5, 128.6, 128.3, 127.0, 117.0, 111.3, 111.0, 59.0, 55.2, 53.7, 53.3,45.5, 39.2, 38.7, 38.0, 37.7. Anal. Calcd. for C₂₂H₂₅NO₂: C, 78.77; H,7.51; N, 4.18. Found: C, 78.76; H, 7.59; N, 4.20.

References

[1] Zimmerman D M, Cantrell B E, Reel J K, Hemrick-Luecke S K, Fuller RW. J. Med. Chem. 1986;29:1517-1520.

[2] Fuller R W. 1986.

[3] Fries D S, de Vries J, Hazelhoff B, Horn A S. J. Med. Chem.1986;29:424.

[4] Barnett C J, Copley-Merriman C R, Maki J. J. Org. Chem.1989;54:4795-4800.

This Example is described in Thomas et al, Tetrahedron Letters, V. 39,7001-7004 (1998), incorporated herein by reference.

Example 6 Selective Delta Opioid Receptor Agonists

Chemistry

Preparation of 3a,b began with reductive amination of1,3-dimethyl-4-piperidone with aniline using titanium (IV) isopropoxide¹which gave 5a,b as a mixture of cis and trans diastereomers in 75% yieldin a ratio of 70:30 (FIG. 17). These were separated by columnchromatography and carried forward independently. These intermediateswere then coupled to the butylated hydroxyanisole (BHA) ester of4-fluorobenzoic acid to give (6a,b) in 91% and 68% yields.² Removal ofthe BHA group was accomplished by transesterification with refluxingsodium methoxide in toluene/N-methylpyrrolidinone followed bysaponification of the methyl ester. The zwitterionic intermediates wereisolated as HCl salts and converted directly into diethylamides usingbenzotriazol-1-yl-oxy-tris-(dimethylamino) phosphoniumhexafluorophosphate (BOP a.k.a. Castro's reagent), diethylamine, andtriethylamine in a tetrahydrofuran (THF) slurry to give 7a and 7b in 90%and 59% yields, respectively. Conversion to the N-allyl group wasaccomplished by treating 7a,b with phenyl chloroformate followed byhydrolysis of the resulting carbamates with potassium hydroxide inisopropyl alcohol. N-Alkylation with allyl bromide then gave 3a,b in 40%and 20% yield, respectively. Stereochemical assignments for 3a were madeusing NOESY spectra and vicinal coupling constants. Proton and carbonassignments were made using a combination of COSY and HETCORR spectra. Alarge coupling constant (J=13.0 Hz) between H5 and H4 indicated adiaxial arrangement between these protons showing that the 4-diarylamineis in the equatorial position. The NOESY spectrum contained a stronginteraction between 5H-axial and the 3-methyl showing that the methylgroup is also axial. The axial equatorial relationship between themethyl and the 4-diarylamine group established the cis relativestereochemistry for 3a.

Biological Activity

The binding affinities of the compounds for the μ, δ, and κ opioidreceptors were determined using competitive binding assays followingpreviously reported procedures.³ The results are listed in Table 12.

Results and Discussion

The radioligand binding data for the compounds 3a,b along withcomparative data for BW373U86 (1) and the two enantiomers ofcis-3-methylfentanyl 4 are shown in Table 12. Compound 3a (the cisisomer) is more potent and more selective for the δ opioid receptorrelative to both the μ and κ opioid receptors than 3b (the transisomer). This difference in selectivity is due to a significantly loweraffinity of the trans isomer for the δ receptor relative to the μ or κopioid receptors. The 11.9 nM K_(i) values for 3a combined with the 1212nM K_(i) value at the μ receptor compare favorably to the K_(i) valuesfor 1 (BW373U86) particularly when one considers that 3a is racemic anddoes not possess all the structural features present in 1, namely the3′-hydroxy group on the aromatic ring and a methyl group comparable tothe piperazine 2-methyl group.

A comparison of the binding data of 3a to that of cis-3-methylfentanyl,particularly the more potent 3R,4S-isomer 4b, is even more striking thanthe comparison of 3a to 1. Compound 4b gave a 3900-fold selectivity forthe μ receptor relative to the δ receptor, whereas 3a possesses a102-fold δ selectivity relative to the μ receptor. This results from asevenfold increase in affinity at the δ receptor (11.9 nM vs. 77.3 nM)and a >60,000-fold loss in affinity at the μ receptor. Thus changing thepropanamido and phenethyl groups present in 4b to the4-diethylcarboamidophenyl and allyl in 3a converts a highly μ-selectivefentanyl analog to a δ-selective ligand. It is highly likely that thegain in δ-receptor potency is due to the change of the propanamido groupof 4 to the diethylcarboxamidophenyl group in 3a. The loss is μ-receptorpotency may be due to both changes. Regardless of the reason for the δopioid receptor selectivity, compound 3a represents a novel ligand forthe δ opioid receptor.

References

(1) Mattson, R. J.; Pham, K. M.; Leuck, D. J.; Cowen, K. A. An improvedmethod for reductive alkylation of amines using titanium(IV)isopropoxide and sodium cyanoborohydride. J. Org. Chem. 1990, 55,2552-2554.

(2) Hattori, T.; Satoh, T.; Miyano, S. Convenient synthesis oftriarylamines via ester-mediated nucleophilic aromatic substitution.Synthesis 1995, 514-518.

(3) Thomas, J. B.; Zheng, X.; Mascarella, S. W.; Rothman, R. B.; Dersch,C. M.; Partilla, J. S.; Flippen-Anderson, J. L.; George, C. F.;Cantrell, B. E.; Zimmerman, D. M.; Carroll, F. I. N-Substituted9β-methyl-5-(3-hydroxyphenyl)morphans are opioid receptor pureantagonists. J. Med. Chem. 1998, 41(21), 4143-4149.

(4) Xu, H.; Kim, C.-H.; Zhu, Y. C.; Weber, R. J.; Rice, K. C.; Rothman,R. B. (+)-cis-Methylfentanyl and its analogs bind pseudoirreversibly tothe mu opioid binding site: Evidence for pseudoallosteric modulation.Neuropharmacology 1991, 30, 455-462.

TABLE 12 Radioligand Binding Results at the μ, δ, and κ Opioid Receptorsfor (±)-4-[(N-Allyl-3-methyl-4-piperidinyl)-phenylamino]N,N-diethylbenzamides Ki (nM ±SD) μ δ κ Compd [3H]DAMGOa [3H]DADLEb [3H]U69,593c μ/δ 1, BW373U86  36 ±3.4  0.91 ± 0.05 NA 40 3a, (±)-cis-isomer 1212 ± 132  11.9 ± 0.9 3284 ±299 102 3b, (±)-trans-isomer 1589 ± 86  126 ± 5  8695 ± 978 13 4a,(3S,4R)-isomer d 30.6 ± 5.13 >1000 NA 0.03 4b, (3R,4S)-isomer d 0.020 ±0.005 77.3 ± 6.7 57.4 ± 6.1 0.0003 ^(a)Ê[3H]DAMGO[(D-Ala2,MePhe4,Gly-ol5)enkephalin]. Tritiated ligand selective for μopioid receptor. bÊ[3H]DADLE [(D-Ala2,D-Leu5)enkephalin]. Tritiatedligand selective for δ opioid receptor. cÊ[3H]U69,593{[3H](5α,7α,8β)-(−)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec-8-yl]benzeneacetamide}.Tritiated ligand selective for κ opioid receptor. d # Data taken fromreference 4. In this experiment, μ sites were labeled with [3H]FOXY([3H]6β-fluoro-6-desoxyoxymorphone).

TABLE 13 Elemental Analyses % Calculated % Found Melting point Compound(C %, H %, N %) (C %, H %, N %) ° C. 7a 66.42, 8.36, 9.68 66.20, 8.31,9.76 193-194 7b 65.73, 8.39, 9.58 65.69, 8.33, 9.62 199-201 3a 69.93,8.24, 9.41 70.06, 8.30, 9.10 221-225.5 3b 69.93, 8.24, 9.41 69.66, 8.31,9.31 177-178

Experimental

(±)-(3RS,4SR)-4-Phenylamino-1,3-dimethylpiperidine (5a) and(±)-(2RS,3RS)-4-Phenylamino-1,3-dimethylpiperidine (5b)

1,3-Dimethyl-4-piperidone (11.77 g, 92.68 mmol), aniline (8.5 mL, 93.4mmol), and titanium isopropoxide (35 mL, 117.7 mmol) were heated at 55°C. for 20 h under a nitrogen atmosphere. The reaction mixture wasallowed to cool and diluted with ethanol (100 mL). Sodium borohydride(5.0 g, 131.6 mmol) was then added, and the reduction was allowed toproceed at room temperature for 4 h. The reaction was quenched byaddition of water, filtered over celite, and the filtrate was washedwith ethanol. After evaporation of the solvent under reduced pressure,the white residue was taken up in ethyl acetate and again filtered overcelite. After evaporation of the solvent under reduced pressure andchromatography on silica gel using ethyl acetate in hexanes (20:80), a70:30 mixture of diastereomers (5a and 5b) (13.80 g, 73%) was obtained.Further separation by chromatography using the same system affordedfirst 5a (8.46 g) as a yellow oil, tentatively assigned a cis relativestereochemistry, and then 5b (2.04 g) as a white solid. 1H NMR 5a(CDCl₃) δ 0.98 (d, 3H, J=6.9 Hz), 1.67-1.89 (m, 2H), 2.03-2.58 (m, 4H),2.18 (s, 3H), 3.41-3.68 (m, 2H), 6.60 (dd, 2H, J=0.9 Hz, J=8.6 Hz), 6.67(dd, 1H, J=0.9 Hz, J=7.3 Hz), 7.15 (t, 2H, J=7.3 Hz). 1H NMR 5b (CDCl₃)δ0.98 (d, 3H, J=6.3 Hz), 1.19-1.48 (m, 1H), 1.58-1.62 (m, 1H), 1.77 (t,1H, J=11.0 Hz), 1.96-2.15 (m, 2H), 2.27 (s, 3H), 2.78-2.93 (m, 3H),3.27-3.41 (m, 1H), 6.57 (dd, 2H, J=1.0 Hz, J=8.6 Hz), 6.66 (dd, 1H,J=1.0 Hz, J=7.3 Hz), 7.12 (t, 2H, J=7.3 Hz).

(±)-2,6-di-tert-Butyl-4-methoxyphenyl-4-[N-{(3RS,4SR)-N,3-dimethyl-4-piperidinyl}-phenylamino]benzoate(6a)

(±)-(3RS,4SR)-4-Phenylamino-1,3-dimethylpiperidine (5a) (3.41 g, 16.72mmol) was dissolved in dry tetrahydrofuran (THF, 13 mL) and dryhexamethylphosphoramide (HMPA, 5 mL), and cooled to −42° C. A 2.5 Msolution of n-butyllithium in hexanes (7.7 mL, 19.25 mol) was slowlyadded, and the reaction mixture was kept at 0° C. for 1 h. The reactionmixture was cannulated into a solution of(2,6-di-tert-butyl-4-methoxyphenyl)-4-fluorobenzoate (6.0 g, 16.76 mmol)in dry THF (13 mL) and dry HMPA (5 mL) at room temperature then heatedto 45-50° C. for 5 h. The reaction mixture was cooled then quenched witha solution of NH₄Cl and diluted with ether. The aqueous layer was madebasic (pH=14) with NaOH 25%, extracted with ether (200 mL), and theethereal layer was washed with water three times. After drying withMgSO₄ and evaporation of the solvents under reduced pressure, a crudebrown oil was afforded. Chromatography on silica gel using ethyl acetatein hexanes (20:80) gave 6a (8.20 g, 91%) as a yellow solid: 1H NMR(CDCl₃) δ 1.21 (d, 3H, J=6.9 Hz), 1.31 (s, 18H), 1.53-1.71 (m, 2H),1.89-1.97 (m, 1H), 2.04 (s, 3H), 2.03-2.32 (m, 1H), 2.59-2.88 (m, 3H),3.81 (s, 3H), 4.00-4.06 (m, 1H), 6.58 (d, 2H, J=9.1 Hz), 6.89 (s, 2H),7.22 (d, 2H, J=8.2 Hz), 7.33 (d, 2H, J=7.2 Hz), 7.41 (t, 1H, J=7.2 Hz),7.97 (d, 2H, J=9.0 Hz).

(±)-2,6-di-tert-Butyl-4-methoxyphenyl-4-[N-{(3RS,4RS)-N,3-dimethyl-4-piperidinyl}phenylamino]benzoate(6b)

(±)-(2RS,3RS)-4-Phenylamino-1,3-dimethylpiperidine (5b) (2.65 g, 12.99mmol) was treated with a 2.5 M solution of n-butyllithium in hexanes (6mL, 15 mol) in dry THF (10 mL) and dry HMPA (4 mL) and coupled with(2,6-di-tert-butyl-4-methoxyphenyl)-4-fluorobenzoate (4.65 g, 12.99mmol) in dry THF (10 mL) and dry HMPA (4 mL) as before. Purificationafforded 6b (4.80 g, 68%) as a yellow solid: 1H NMR (CDCl₃) δ 1.07 (d,3H, J=5.6 Hz), 1.31 (s, 18H), 1.63-2.15 (m, 5H), 2.25 (s, 3H), 2.85-2.97(m, 2H), 3.68-3.78 (m, 1H), 3.81 (s, 3H), 6.63 (d, 2H, J=9.1 Hz), 6.88(s, 2H), 7.19 (d, 2H, J=7.1 Hz), 7.33 (t, 1H, J=7.1 Hz), 7.44 (t, 2H,J=7.7 Hz), 7.95 (d, 2H, J=9.1 Hz).

(±)-4-[N-{(3RS,4SR)-N,3-Dimethyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(7a)

(±)-2,6-Di-tert-butyl-4-methoxyphenyl-4-[N-{(3RS,4SR)-N,3-dimethyl-4-piperidinyl}phenylamino]benzoate(6a) (6.5 g, 11.99 mmol) in toluene (150 mL) and N-methylpyrrolidinone(NMP, 40 mL) was added to freshly prepared sodium methoxide (120 mmol)and heated at reflux for 4 h. After evaporation of the toluene underreduced pressure, the residue was dissolved in a mixture of MeOH and H₂O(12:1, 150 mL) and heated at reflux for 1 h. After evaporation of thealcohol, the residue was taken up in water (400 mL) and extracted withhexanes (2×100 mL). The aqueous layer was made acidic (pH=1) with 10%HCl, saturated with NaCl, and extracted with a mixture of CH₂Cl₂ and THF(3:1, 5′ 200 mL). After drying over Na₂SO₄, the solvents were evaporatedunder reduced pressure. This was then treated with diethylamine (1.2mL), benzotriazol-1-yl-oxy-tris-(dimethylamino)phosphoniumhexafluorophosphate (BOP a.k.a. Castro's reagent) (5.0 g, 11.31 mmol) ),and triethylamine (4.2 mL) in THF (100 mL) for 30 min. The reactionmixture was next diluted with ether (300 mL), washed with water (2×75mL), saturated NaHCO₃ (75 mL), and dried over Na₂SO₄ providing a blackoil following evaporation of the solvents under reduced pressure.Chromatography on silica gel using hexanes/ethylacetate/ethanol/triethylamine (60:40:2:2) afforded 7a (4.10 g, 90%) as ayellow liquid. This was converted to the hydrochloride salt using 1N HClin ether. ¹H NMR (CD₃OD) δ 1.07-1.38 (m, 12H), 1.42-1.61 (m, 1H),1.68-1.92 (m, 1H), 2.86 (s, 3H), 3.03-3.21 (m, 1H), 3.27-3.60 (m, 6H),4.30-4.48 (m, 1H), 6.80 (d, 2H, J=8.3 Hz), 7.14 (d, 2H, J=7.7 Hz), 7.26(t, 3H, J=7.5 Hz), 7.40 (t, 2H, J=7.4 Hz); ¹³C NMR (CD₃OD) δ 12.2, 25.6,30.4, 44.5, 55.7, 56.0, 60.2, 119.4, 127.4, 128.8, 130.7, 130.8, 146.1,150.8, 173.8. Anal. (C₂₄H₃₄ClN₃O.H₂O): C, H, N.

(±)-4-[N-{(3RS,4RS)-N,3-Dimethyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(7b)

(±)-2,6-Di-tert-butyl-4-methoxyphenyl-4-[N-{(3RS,4RS)-N,3-dimethyl-4-piperidinyl}phenylamino]benzoate(6b) (7.38 g, 13.62 mmol) was transesterified with sodium methoxide (135mmol) in toluene (150 mL) and NMP (40 mL) and then hydrolyzed with MeOHand H₂O (12:1, 165 mL) as before. The resulting acid was dissolved inTHF (200 mL) with triethylamine (5 mL), diethylamine (2 mL), and BOPreagent (6.1 g, 13.80 mmol) as above. Work-up and chromatography onsilica gel as above afforded 7b (3.02 g, 59%) as a yellow liquid.Conversion to the hydrochloride salt was done with 1 N HCl in ether. ¹HNMR (CD₃OD) δ 1.10-1.25 (m, 12H), 1.76-2.28 (s, 3H), 2.99 (t, 1H, J=12.5Hz), 3.12-3.29 (m, 1H), 3.31-3.58 (m, 7H), 4.12-4.29 (m, 1H), 6.78 (d,2H, J=8.8 Hz), 7.18 (d, 2H, J=7.3 Hz), 7.22 (d, 2H, J=8.8 Hz), 7.33 (t,1H, J=7.4 Hz), 7.48 (t, 2H, J=7.5 Hz); ¹³C NMR (CD₃OD) δ 16.1, 29.0,35.3, 43.8, 55.3, 58.7, 60.7, 116.9, 127.3, 127.8, 129.1, 130.7, 131.2,144.0, 152.0, 173.9. Anal. (C₂₄H₃₄ClN₃O.1.25H₂O): C, H, N.

(±)-4-[N-{(3RS,4SR)-N-Allyl-3-methyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(3a).

(±)-4-[N-{(3RS,4SR)-N,3-Dimethyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(7a) (4.1 g, 10.82 mmol) was treated with phenyl chloroformate (1.25 mL,11.13 mmol) in 1,2-dichloroethane (35 mL) at room temperature for 24 h.The reaction was quenched with water and NaOH 30% then extracted withCHCl₃. After drying over Na₂SO₄ and evaporation of the solvents underreduced pressure, the crude product was chromatographed on silica gel togive a mixture of starting material and product which was then treatedwith methanol (100 mL), water (60 mL), isopropanol (50 mL), and NaOH 50%(30 mL) at reflux for 5 h. The alcohols were evaporated under reducedpressure, and the aqueous layer was extracted with CHCl₃/THF (3:1).After drying with Na₂SO₄, the solvents were evaporated under reducedpressure. Chromatography on silica gel using hexanes/ethylacetate/ethanol/triethylamine (50:50:3:3) afforded starting material(6a), (548 mg, 13%), as a yellow oil followed by the N-demethylatedmaterial (924 mg, 30%) as a yellow oil using ethanol/triethylamine(80:20) as eluent. The latter material was dissolved in ethanol (40 mL)and treated with allyl bromide (220 μL, 2.54 mmol) and K₂CO₃ (1.0 g,7.24 mmol) at room temperature for 24 h. After evaporation of theethanol under reduced pressure, the residue was chromatographed onsilica gel using hexanes/ethyl acetate/ethanol/triethylamine (50:50:3:3)to give 3a (950 mg, 93%) as a yellow oil. This was converted to thehydrochloride as previously described: ¹H NMR (δ₄-MeOH) 1.18 (m, 6H),1.23 (d, 3H, J=7.4 Hz), 1.54 (d, 1H, J=13.0 Hz), 1.81 (ddd, 1H, J=13.0Hz, 13.0 Hz, 11.0 Hz), 2.91 (m, 1H), 3.09 (dd, 1H, J=13.0 Hz, 13.0 Hz),3.44 (m, 7H), 3.75 (d, 1H, 7.4 Hz), 4.38 (d, 1H, J=13.5 Hz), 5.59 (d,1H, J=9.9 Hz), 5.60 (d, 1H, J=17.0 Hz), 6.00 (ddd, 1H, J=17.0 Hz, 17.0Hz, 7.4 Hz), 6.79 (d, 2H, J=8.5 Hz), 7.14 (d, 2H J=8.0 Hz), 7.23 (d, 2H,J=8.5 Hz), 7.28 (dd, 1H, J=8.0 Hz, 8.0 Hz), 7.40 (dd, 2H, J=8.0 Hz, 8.0Hz). ¹³C NMR (d4-MeOH) 11.3, 13.2 (broad), 24.5, 29.3, 45.0 (broad),52.4, 55.2, 56.7, 59.6, 118.3, 125.9, 126.4, 126.6, 127.7, 129.7, 145.0,149.8, 172.7. Anal. (C₂₆H₃₆ClN₃O.0.25H₂O): C, H, N.

(±)-4-[N-{(3RS,4RS)-N-Allyl-3-methyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(3b).

(±)-4-[N-{(3RS,4RS)-N,3-Dimethyl-4-piperidinyl}phenylamino]-N,N-diethylbenzamide(7b) (502 mg, 1.32 mmol) was treated with phenyl chloroformate (170 μL,1.51 mmol) in 1,2-dichloroethane (4 mL) at room temperature for 24 h.The product was worked-up as above, and chromatography on silica gelusing hexanes/ethyl acetate/ethanol/triethylamine (75:25:1:1) affordedfirst the phenylcarbamate as a white solid followed by the startingmaterial (117 mg, 23%) as a yellow liquid. The carbamate was treatedwith methanol (20 mL), water (15 mL), isopropanol (10 mL), and NaOH 50%(5 mL) and worked-up as above to give the crude N-demthylatedintermediate as a yellow oil. This was dissolved in ethanol (5 mL) andtreated with allyl bromide (100 μL, 1.15 mmol) and K₂CO₃ (500 mg, 3.62mmol) for 16 h at room temperature. Work-up and purification as aboveafforded 3b (70 mg, 15% overall) as a yellow oil. This was converted tothe hydrochloride salt as previously described: ¹H NMR (CD₃OD) δ1.10-1.26 (m, 9H), 1.741.96 (m, 1H), 1.98-2.29 (m, 2H), 2.88-3.01 (m,1H), 3.10-3.22 (m, 1H), 3.35-3.61 (m, 7H), 3.73 (d, 2H, J=7.3 Hz), 4.20(dt, 1H, J=3.4 Hz, J=11.5 Hz), 5.55 (s, 1H), 5.61 (d, 1H, J=5.4 Hz),5.85-6.03 (m, 1H), 6.78 (d, 2H, J=8.8 Hz), 7.19 (d, 2H, J=7.8 Hz), 7.23(d, 2H, J=8.8 Hz), 7.34 (t, 1H, J=7.4 Hz), 7.51 (t, 2H, J=7.6 Hz); ¹³CNMR (CD₃OD) δ 11.9, 13.9, 16.2, 28.9, 35.2, 52.9, 58.3, 59.1, 60.1,117.0, 126.8, 127.6, 127.8, 129.0, 130.7, 131.2, 144.1, 151.8, 173.9.Anal. (C₂₆H₃₆ClN₃O.0.25H₂O): C, H, N.

Example 7 N-Alkyl-4β-methyl-5-phenylmorphans

Summary

A convergent, highly stereoselective synthetic approach toN-alkyl-4β-methyl-5-phenylmorphans has been developed utilizingalkylation of the metalloenamine ofN-alkyl-1,2,3,6-tetrahydro-4-phenylpyridines with2-(chloromethyl)-3,5-dioxahex-1-ene (Okahara's reagent) followed byClemmensen reduction.

Chemistry

4β-methyl-(3-hydroxyphenyl)morphans were stereoselectively synthesizedas shown in FIG. 18. Alkylation of 8¹ with2-(chloromethyl)-3,5-dioxohex-1-ene (Okahara's reagent)² followed byhydrolysis of the methoxymethyl protecting group (FIG. 18) gives enamine12. In the alkylation reaction, the methyl group apparently exerts apowerful directing effect since enamine 12 is the sole product.Cyclization under acidic conditions occurs regiospecifically on carbon 1(phenylmorphan numbering) due to the specific migration of the doublebond during the alkylation reaction. Furthermore, since the oxidationstate of carbon 7 does not change following cyclization, no hydrideshift occurs and the stereogenic center of carbon 4 is preservedproviding 2,4β-dimethyl-7-oxo-5-(3-methoxyphenyl)morphan (13) as asingle diastereomer. Clemmensen reduction³ and deprotection of thephenol⁴ then completes the synthesis of2,4β-dimethyl-5-(3-hydroxyphenyl)morphan (3, R=CH₃) in 48% overall yieldfrom 8. The stereochemical assignments for 3 (R=CH₃) were made usingNOESY spectra of a sealed degassed sample obtained with mixing time of1.500 sec and an interpulse delay of 4 sec.⁵ A strong interactionbetween the 4-methyl group and the 9β and 3β protons established the4β-stereochemistry.

A requirement for significant quantities of 3 and its analogs for invivo testing coupled with the usefulness of intermediates similar to 13in the preparation of delta opioid receptor selective agonists,^(6,7)suggested improving the overall yield of the alkylation/cyclizationsequence. Experimentation with a variety of conditions revealed thataddition of the metalloenamine of 8 to a solution of Okahara's reagent,rather than the reverse, gave much higher yields in the metalloenaminealkylation. In combination with an extractive workup to removeformaldehyde (formed by hydrolysis of the methoxymethyl group) andcyclization conditions similar to those defined by Bonjoch et al.,⁸ theoverall yield of the alkylation/cyclization sequence for 13 wassignificantly improved (75% for this work vs. 30% using the one-potprocedure).⁹

In summary, this example provides a highly diastereoselective syntheticapproach to the N-alkyl-4β-methyl-5-(3-hydroxyphenyl)morphan system aswell as providing a higher yielding route to the useful7-oxo-5-(3-methoxyphenyl)morphan opioid intermediates.

References and Notes

1. Werner, J. A.; Cerbone, L. R.; Frank, S. A.; Ward, J. A.; Labib, P.;Tharp-Taylor, K W.; Ryan, C. W. J. Org. Chem. 1996, 61, 587-597.

2. Gu, X.-P.; Nishida, N.; Ikeda, I.; Okahara, M. J. Org. Chem. 1987,52, 3192-3196.

3. Bosch, J.; Bonjoch, J. Heterocycles 1980, 14, 505.

4. Rice, K. C. J. Med. Chem. 1977, 20, 164-165.

5. Proton assignments for 3 were made using a combination of COSY andHETCORR spectra. ¹H NMR (d4-MeOH) δ 0.782 (d, 3H, J=7.5 Hz), 1.65 (m,1H), 1.78 (m, 1H), 1.85 (m, 1H), 2.02 (d, 1H, J=15 Hz), 2.08 (m, 1H),2.24 (m, 1H), 2.29 (m, 1H), 2.46 (q, 1H, J=7.5 Hz), 2.54 (d, 1H, J=15.0Hz), 2.92 (s, 3H), 3.26 (d, 1H, J=13.6 Hz), 3.70 (m, 1H), 3.86 (dd, 1H,J=13.6 Hz, 5.3 Hz), 6.67 (m, 1H), 7.15 (t, 3H, J=7.9 Hz).

6. Bertha, C. M.; Flippen-Anderson, J. L.; Rothman, R. B.; Porreca, F.;Davis, P.; Xu, H.; Becketts, K.; Cha, X.-Y.; Rice, K. C. J. Med Chem.1995, 38, 1523-1537.

7. Bertha, C. M.; Ellis, M.; Flippen-Anderson, J. L.; Porreca, F.;Rothman, R. B.; Davis, P.; Xu, H.; Becketts, K.; Rice, K. C. J. Med.Chem. 1996, 39, 2081-2086.

8. Bonjoch, J.; Casamitjana, N.; Gracia, J.; Bosch, J. Tetrahedron Lett.1989, 30, 5655-5658.

9. General Procedure for Alkylation/Cyclization Sequence: (CAUTION: Readreference 4 and references cited therein for information onN-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, MPTP and its derivatives.)The appropriate tetrahydropyridine derivative (1 eq) is dissolved in THF(20 mL/g) and cooled to −10° C. n-Butyl lithium (1.6M in hexanes) isslowly added until a red color is maintained followed by an addition of1.1 eq. This material is stirred for 1 h at −10° C. and then cannulatedquickly into a solution of Okahara's reagent (distilled to high purity)in THF (15 mL/g, 1.1 eq) at −78° C. followed by stirring for 2 h. Thetemperature should be kept below −30° C. during cannulation. Thismaterial is then poured into 2N HCl and extracted twice with ethylether. The aqueous layer is allowed to stand for 15 min followed byaddition of 50% NaOH to pH 14 and extraction (3×) with ethyl ether. Theether is then washed (1N NaOH, H₂O) and the solvent removed under vacuumThe resulting residue of product and water is dissolved in MeOH (30mL/g) and nitrogen is bubbled through the solution for 5 min. To this isadded concentrated HCl (2 mL/g), and the mixture is allowed to stand atroom temperature until the reaction is complete as indicated by TLC (upto 7 days). TLC condition: SiO₂; elution with 50% (80% CHCl₃:18%CH₃OH:2% NH₄OH) in CHCl₃. Detection: 5% phosphomolybdic acid in ethanol.All compounds gave satisfactory ¹H and ¹³C NMR and mass spectra.

This Example is described in Thomas et al, Tetrahedron Letters, Vol. 40,pp. 403-406 (1999), incorporated herein by reference.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

All references cited above are incorporated into this application byreference in their entirety unless noted otherwise.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:
 1. A 4β-methyl or a 9β-methyl compound represented by formula (III):

where R₁ is an alkyl group or an aralkyl group; R₂ is hydrogen, an alkyl group, an aralkyl group, ═O, —NH₂, —NHR, —N(R)₂, —NHC(O)R, —NRC(O)R, —NHC(O)R₅, or —NRC(O)R₅; R₃ and R₄ may be hydrogen or methyl, with the proviso that when R₃ is methyl then R₄is hydrogen and when R₃ is hydrogen then R₄is methyl; each R is, independently, an alkyl group, an aryl group, or an aralkyl group; and R₅ is

each X is, independently, halogen, —OH, —OR, an alkyl group, an aryl group, —NH₂, —NHR, —N(R)₂, —CF₃, —CN, —C(O)NH₂, —C(O)NHR, or —C(O)N(R)₂; each R is, independently, as defined above; n is 0 or an integer from 1 to 5; and R_(a) is hydrogen or an alkyl group, or a pharmaceutically acceptable salt thereof.
 2. The compound of claim 1, wherein R₁ is a C₁₋₈ alkyl group or an aryl-C₁₋₄ alkyl group; R₃ is methyl; and R₄ is hydrogen.
 3. The compound of claim 2, wherein R₁ is a C₁₋₈ alkyl group or an phenyl-C₁₋₄ alkyl group.
 4. The compound of claim 1, wherein R₁ is a C₁₋₈ alkyl group or an aryl-C₁₋₄ alkyl group; R₃ is hydrogen; and R₄ is methyl.
 5. The compound of claim 4, wherein R₁ is a C₁₋₈ alkyl group or an phenyl-C₁₋₄ alkyl group.
 6. The compound of claim 1, wherein R₂ is ═O.
 7. A method of binding opioid receptors, comprising administering an effective amount of the compound of claim 1 to a mammalian subject in need thereof.
 8. The compound of claim 1, wherein R₁ is an aralkyl group; R₂ is —NHC(O)R; R₃ is hydrogen; R₄ is methyl; R is an aralkyl group.
 9. The compound of claim 8, wherein R₁ is a phenyl-C₁₋₄ alkyl group; and R is a phenyl-C₁₋₈ alkyl group. 